Direct Answer
Under 14 CFR §135.145, a Part 135 operator must fly a proving test — at least 25 hours acceptable to the Administrator — before operating a two-pilot non-turbojet or a turbojet aircraft it has not proven before, and must complete a validation test to add such an aircraft of a new make or design or to gain certain new operating authorizations (operations outside U.S. airspace, Class II navigation, and special performance or operational authorizations).
The 25 proving hours must include five hours of night time if night flights are to be authorized, five instrument approach procedures if IFR flights are to be authorized, and entry into a representative number of en route airports as determined by the Administrator. Passengers may not be carried during proving tests except those needed to make the tests and those the Administrator designates to observe them — though pilot training may be conducted during the tests. See 14 CFR §135.145.
A proving or validation test generates its own records — the test plan, the flight-time and approach logs, the FAA's acceptance — and the operations specifications authorization that follows is what actually lets the aircraft or operation enter revenue service. This is a separate step from the conformity inspection that adds the specific tail to your fleet; for that, see adding an aircraft to a Part 135 certificate.
Why Some Aircraft Have to Be Flown Before They Earn
Most of what stands between a newly purchased aircraft and a revenue trip is paperwork — registration, airworthiness, a conformity inspection, an operations specifications amendment. But for certain aircraft, paperwork is not enough. When a certificate holder reaches for a category of aircraft it has never operated under Part 135 — a turbojet, or a two-pilot type — the FAA wants to see the operator actually fly it, in a structured demonstration, before it will authorize revenue service. That demonstration is the proving test. Its lighter-weight relative, the validation test, covers new kinds of operation: flying outside U.S. airspace, using Class II navigation, or holding a special operational authorization.
Both live in one short section, 14 CFR §135.145, and both matter to the records side of compliance because a test that the FAA accepts is itself a permanent part of your certificate's history. This article walks the section paragraph by paragraph: how proving differs from validation, what the 25 hours actually contain, exactly when an aircraft or operation triggers a test, the passenger prohibition during proving, and — the part that outlives the flying — the records the test generates and the operations specifications authorization that follows. For the broader recordkeeping picture this all sits inside, start with what records a Part 135 operator must keep.
Proving vs. Validation: Two Tools in One Section
Section 135.145 packs two related but distinct requirements into one place, and operators new to fleet or capability growth often blur them. The cleanest way to hold them apart is by what each is fundamentally testing — and whether it requires you to fly.
Proving test — §135.145(a) & (b)
A hands-on demonstration that the operator can safely run a particular kind of aircraft it has not proven before. It is built around flying: at least 25 hours acceptable to the Administrator, with night and instrument-approach elements tied to the authorizations sought, and entry into a representative number of en route airports.
- Applies to a two-pilot non-turbojet (VFR) and to a turbojet airplane.
- Requires actual flight hours — there is no paper substitute for the proving hours.
- No passengers except those needed for, or designated to observe, the tests.
Validation test — §135.145(d) & (e)
A determination that the operator is capable of conducting operations safely and in compliance with applicable regulatory standards. It is required for specific authorizations rather than for flying-hour accumulation, and §135.145(e) allows it to be met without an actual flight where competence can otherwise be demonstrated.
- Adding a two-pilot/turbojet aircraft of a make or design not before proved or validated.
- Operations outside U.S. airspace; Class II navigation authorizations.
- Special performance or operational authorizations.
Two more paragraphs tie the section together. Section 135.145(f) allows proving tests and validation tests to be conducted simultaneously when appropriate — useful when a new type and a new operating authorization arrive together. And §135.145(g) lets the Administrator authorize deviations from the section where special circumstances make full compliance unnecessary. The throughline: the proving test is about flying the aircraft, the validation test is about demonstrating capability, and in both cases the standard is what is acceptable to the Administrator — the FAA, not the operator, sets the bar and judges whether it has been cleared.
Inside the 25 Hours: What a Proving Test Actually Contains
The number everyone remembers from §135.145 is 25 hours — but the figure is a floor, and what fills it is shaped by the authorizations you are seeking. Paragraph (a) prohibits operating a two-pilot non-turbojet aircraft not previously proved unless the certificate holder has proved such an aircraft in Part 135 operations in at least 25 hours of proving tests acceptable to the Administrator, and paragraph (b) imposes the same at-least-25-hour requirement for a turbojet airplane not previously proven. Within those hours, the rule names three components:
Five hours of night time — if night flights are to be authorized
The night element is conditional: §135.145(a)(1) and (b)(1) require five hours of night time only if night flights are to be authorized. If you are not seeking night authorization for the aircraft, this element does not attach — but most charter operators will want it, which means budgeting the night hours into the proving program from the start.
Five instrument approach procedures — if IFR flights are to be authorized
Likewise conditional: §135.145(a)(2) and (b)(2) require five instrument approach procedures under simulated or actual conditions, only if IFR flights are to be authorized. For an aircraft intended for IFR revenue service — nearly all of them — these approaches are part of the proving demonstration the FAA evaluates.
Entry into a representative number of en route airports
Section 135.145(a)(3) and (b)(3) require entry into a representative number of en route airports as determined by the Administrator. This is not a fixed count — the FAA determines what is representative for your operation, which lets the proving program reflect the kind of route structure and airports the aircraft will actually serve.
25 hours is a minimum, not a target
The phrase the rule uses is "at least 25 hours of proving tests acceptable to the Administrator." Both halves matter. The 25 hours is a floor the FAA can build on for a complex, unusual, or higher-risk operation, and acceptable to the Administrator means the content, the conditions, and the conduct of the proving are judged by the FAA — not satisfied by simply logging the time. Build the proving program with your assigned FAA office, not from a number alone.
One more point of precision: the proving requirement is about the aircraft category, not the individual airframe. Once your certificate has proved a given category — a particular turbojet, say — adding another aircraft of the same make or similar design generally does not require re-proving. The proving hours establish the operator's capability with that kind of aircraft; the conformity inspection (covered separately, below and in the linked guide) handles the individual tail.
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When an Aircraft or Operation Actually Triggers a Test
The most common §135.145 question is also the most consequential to the calendar: does this add require a test or not? Get it wrong in the optimistic direction and you have planned revenue around an aircraft that cannot fly it; get it wrong in the pessimistic direction and you have built schedule and cost into a project that did not need them. The triggers are specific.
A two-pilot non-turbojet your certificate has never proved
§135.145(a) + (d)(1)An aircraft (other than a turbojet) for which two pilots are required by the chapter for operations under VFR, not previously proved in Part 135 operations, triggers the at-least-25-hour proving requirement in (a) — and validation under (d)(1) where it (or one of the same make or similar design) has not been previously proved or validated.
A turbojet airplane your certificate has never proven
§135.145(b) + (d)(1)A turbojet airplane not previously proven triggers the parallel at-least-25-hour proving requirement in (b). Adding the operator's first jet is the textbook proving case, and it is also the textbook §119.51(c) 90-day filing — the two requirements travel together.
Operations outside U.S. airspace
§135.145(d)(2)Validation testing is required for operations outside U.S. airspace — a trigger that is about the operating environment, not the aircraft type. A single-pilot piston otherwise exempt from proving can still face a validation requirement when the operation crosses into this category.
Class II navigation authorizations
§135.145(d)(3)Authorizations for Class II navigation require validation testing under (d)(3). This is again capability-based: the FAA is validating that the operator can conduct that navigation safely and in compliance, by methods acceptable to the Administrator.
Special performance or operational authorizations
§135.145(d)(4)Special performance or operational authorizations are a validation trigger under (d)(4). Because §135.145(e) permits validation without an actual flight where competence can be demonstrated, some of these may be satisfiable through a demonstration acceptable to the FAA rather than a test flight — but the determination belongs to the Administrator.
What does NOT trigger a test
Adding another aircraft of a make and model — or a similar design — your certificate has already proved or validated generally does not re-trigger §135.145. That same-type add is the ordinary 15-day OpSpecs amendment and conformity inspection, not a proving project. The dividing line in (d)(1) is whether the aircraft, or one of the same make or similar design, has been previously proved or validated in operations under this part. The FAA makes that determination — when in doubt, ask before you assume.
This is also why the filing window changes. Under 14 CFR §119.51(c), an operator-requested OpSpecs amendment is filed at least 15 days before the proposed effective date in ordinary cases — but at least 90 days for, among other things, the initial introduction of aircraft not before proven for use in air carrier or commercial operator operations. The 90-day window exists precisely because a never-before-proven aircraft can carry a proving or validation requirement, and the FAA needs runway to plan and observe it. The mechanics of that amendment, the conformity inspection, and the records package live in the companion guide to adding an aircraft to a Part 135 certificate.
Who Can Ride: Passengers and Cargo During Proving
A proving test is a demonstration the FAA is evaluating, not a revenue flight, and §135.145(c) draws that line in passenger terms. The paragraph provides that no certificate holder may carry passengers in an aircraft during proving tests, except those needed to make the tests and those designated by the Administrator to observe the tests — and it adds that pilot flight training may be conducted during the proving tests. Three consequences follow.
You cannot sell seats on a proving flight
Because passengers during proving are limited to those needed to make the tests and those the Administrator designates to observe, the proving hours cannot carry revenue passengers. Plan the proving program as a cost of entry to the new category, not as early revenue.
Observers and test personnel are the allowed exceptions
The two carve-outs are people performing the test (the required crew and test personnel) and FAA-designated observers. Treat the manifest on a proving flight as part of the record — who was aboard and in what role is exactly the kind of detail a later review can examine.
Pilot training can be folded in
Section 135.145(c) expressly permits conducting pilot flight training during the proving tests — a practical efficiency, since crews qualifying on a new type and the proving demonstration often involve the same flying. The training records that result are their own compliance artifact.
On cargo, do not assume an allowance the rule does not state
The §135.145(c) prohibition is written about passengers, and the paragraph does not separately spell out a revenue-cargo allowance during proving. Do not read silence as permission. If your proving program contemplates carrying any cargo, confirm what your test plan and your assigned FAA office permit — and keep the proving hours framed as a demonstration the FAA is assessing rather than a revenue opportunity. When the rule is silent on a detail, the safe course is to verify with your FSDO, not to infer.
If your operation is a passenger-carrying charter, the passenger-side records the new type will live under once it is in service — briefings, cabin safety, and the rest — are covered in the guide to Part 135 passenger briefing and cabin safety records. Proving is the gate; those obligations are what waits on the other side of it.
The Records a Proving or Validation Test Generates
The flying ends; the file does not. A proving or validation test produces a discrete set of documents that becomes part of your certificate's permanent history and that a later FAA review — or a buyer's due diligence — can reach for years afterward. Section 135.145 does not itself prescribe a retention table for these, but they fold into the operator's recordkeeping obligations and, critically, into the operations specifications that carry the resulting authorization. Here is what the test leaves behind.
The Proving / Validation Test Plan
§135.145(a)–(e) (program acceptable to the Administrator)What it is
The plan or program the FAA accepts before the test: the aircraft and authorizations in scope, the hours and elements to be flown (night, instrument approaches, en route airports), the crew and observers, and the test methods for any validation component. Because the rule keys everything to what is acceptable to the Administrator, the accepted plan is the document that defines what the test had to demonstrate.
How FileFlo tracks it
FileFlo classifies the accepted test plan against the aircraft type, so the controlling document for the proving event is indexed and retrievable rather than buried in a project folder.
Flight-Time, Night, and Instrument-Approach Logs
§135.145(a)(1)–(3) / (b)(1)–(3)What it is
The records demonstrating the 25-plus hours were flown and that the conditional elements were satisfied: total proving hours, the five hours of night time where night authorization is sought, the five instrument approaches where IFR authorization is sought, and the representative en route airports entered. These are the evidence that the floor in (a)/(b) and its components were actually met.
How FileFlo tracks it
FileFlo indexes the proving flight logs to the aircraft and surfaces them alongside the plan and the FAA acceptance, so the demonstration is provable as a set, not a scavenger hunt.
Validation Test Methods and Results
§135.145(d)–(e)What it is
For a validation requirement, the methods used — flight or otherwise — and their results. Section 135.145(e) allows validation without an actual flight where competence and compliance can be demonstrated by methods acceptable to the Administrator, so the record may be a documented demonstration of capability rather than a flight log. Either way, it has to show the standard was met by an accepted method.
How FileFlo tracks it
FileFlo classifies validation-test documentation against the specific authorization it supports, keeping the capability evidence linked to the operation it unlocked.
FAA Acceptance and Correspondence
FAA practice under §135.145 / Part 119What it is
The FAA's acceptance of the proving or validation tests, and the correspondence around it, document that the demonstration satisfied the Administrator. This is the bridge between the test and the authorization — the FAA does not issue the operations specifications authorization until it is satisfied the test was acceptable.
How FileFlo tracks it
FileFlo stores the acceptance and related correspondence with the aircraft and authorization, so the chain from test to authorization is intact in one place.
The Operations Specifications Authorization
§119.51 / §119.5What it is
The OpSpecs revision that follows a successful test is what actually permits the aircraft or operation to enter revenue service. It is issued under §119.51, and §119.5(g) prohibits operating without, or in violation of, appropriate operations specifications — so this document, not the completion of the flying, is the legal authority to operate. Treat it as the capstone record of the entire proving/validation effort.
How FileFlo tracks it
FileFlo version-tracks the OpSpecs authorization and ties it back to the proving and validation records that earned it — the audit-ready throughline from demonstration to authority to fly.
Crew Training Records from the Proving Flights
§135.63(a)(4) / Subpart H training rulesWhat it is
Because §135.145(c) permits pilot flight training during proving, the proving event often produces crew qualification and training records for the new type as well. Those records live under the operator's pilot recordkeeping and training-program obligations, and they outlast the proving event — the crews keep flying the aircraft long after the proving is signed off.
How FileFlo tracks it
FileFlo classifies the resulting pilot and training records to each crewmember and tracks their recurring currency, so qualification on the new type stays provable after the proving file closes.
Related records the new type carries into service: Part 135 pilot records · training program recordkeeping · check airman / flight instructor records · MEL / CDL records · GOM / GMM manual requirements · CAMP recordkeeping
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Frequently Asked Questions
What does 14 CFR §135.145 require?
Section 135.145 governs aircraft proving and validation tests. Paragraph (a) prohibits a certificate holder from operating an aircraft (other than a turbojet) for which two pilots are required by the chapter for operations under VFR if it has not previously proved such an aircraft in operations under Part 135 in at least 25 hours of proving tests acceptable to the Administrator, including five hours of night time if night flights are to be authorized, five instrument approach procedures under simulated or actual conditions if IFR flights are to be authorized, and entry into a representative number of en route airports as determined by the Administrator. Paragraph (b) imposes the same 25-hour proving requirement, with the same night and instrument-approach elements, on turbojet airplanes not previously proven. Paragraph (c) prohibits carrying passengers during proving tests except those needed to make the tests and those designated by the Administrator to observe them, though pilot flight training may be conducted during the tests. Paragraph (d) describes when validation testing is required, and paragraphs (e) through (g) cover test methods, simultaneous testing, and deviations.
What is the difference between a proving test and a validation test?
They are two distinct tools in the same section. A proving test under §135.145(a) and (b) is the hands-on demonstration — at least 25 hours of flying acceptable to the Administrator — that a certificate holder can safely operate a particular kind of aircraft (a two-pilot non-turbojet, or a turbojet) it has not proven before. A validation test under §135.145(d) determines that a certificate holder is capable of conducting operations safely and in compliance with applicable regulatory standards, and is required for specific authorizations: adding a two-pilot or turbojet aircraft (or one of the same make or similar design) not previously proved or validated, operations outside U.S. airspace, Class II navigation authorizations, and special performance or operational authorizations. The key practical contrast is in §135.145(e): validation tests must use test methods acceptable to the Administrator, and actual flights may not be required when an applicant can demonstrate competence and compliance without conducting a flight. A proving test is fundamentally about flying the hours; a validation test is about demonstrating capability, sometimes on paper. Under §135.145(f), the two may be conducted simultaneously when appropriate.
How many proving hours does the FAA require under §135.145?
At least 25 hours. Under §135.145(a), a two-pilot non-turbojet aircraft that has not been previously proved requires at least 25 hours of proving tests acceptable to the Administrator, and §135.145(b) applies the same at-least-25-hour floor to a turbojet airplane not previously proven. Inside those 25 hours the rule calls out specific elements tied to the authorizations sought: five hours of night time if night flights are to be authorized, and five instrument approach procedures under simulated or actual conditions if IFR flights are to be authorized. The rule also requires entry into a representative number of en route airports as determined by the Administrator. Read the 25 hours as a minimum, not a target — the Administrator determines what proving is acceptable, and the figure is a floor the FAA can build on for a complex or unusual operation.
Can we carry paying passengers or revenue cargo during a proving test?
No passengers, with a narrow exception. Section 135.145(c) provides that no certificate holder may carry passengers in an aircraft during proving tests except those needed to make the tests and those designated by the Administrator to observe the tests; it also provides that pilot flight training may be conducted during the proving tests. That means the proving hours are non-revenue with respect to passengers — you cannot sell seats on a proving flight. The rule text addresses passengers and does not, in §135.145(c), set out a separate revenue-cargo allowance, so do not assume one — confirm what your proving test plan and your assigned FAA office permit for any cargo carried, and treat the proving hours as a demonstration the FAA is evaluating, not a revenue opportunity.
When does adding an aircraft trigger proving or validation tests?
Only when the aircraft is genuinely new ground for your certificate. Adding another aircraft of a make and model you have already proven generally does not re-trigger §135.145 testing — §135.145(d)(1) ties validation testing to an aircraft that, or an aircraft of the same make or similar design that, has not been previously proved or validated in operations under this part. The triggers are: a two-pilot non-turbojet or a turbojet airplane your certificate has never proven (proving tests under (a) or (b), and validation under (d)(1)); operations outside U.S. airspace; Class II navigation authorizations; and special performance or operational authorizations (each a validation trigger under (d)). A single-pilot piston already common in Part 135 service triggers none of this. The FAA — not the operator — makes the determination of whether a given aircraft or operation requires testing and what scope it takes. This is also why §119.51(c) sets a 90-day filing window for the initial introduction of aircraft not before proven, versus 15 days for an ordinary same-type add.
What records does a proving or validation test generate, and who keeps them?
A proving or validation test produces its own evidence trail that becomes part of the certificate's permanent history: the proving test plan or program accepted by the FAA, the flight logs and time records documenting the hours flown (including the night and instrument-approach elements and the en route airports entered), any validation-test methods and results, and the FAA's acceptance of the tests and the resulting operations specifications authorization. None of these is a substitute for the routine recordkeeping that continues afterward — the aircraft and pilot records under §135.63, the maintenance status records, the training records, and the OpSpecs themselves. The operator keeps these records; the FAA reviews them. Because §119.5(g) prohibits operating without, or in violation of, an appropriate certificate and appropriate operations specifications, the OpSpecs authorization that follows a successful test is the document that actually lets the aircraft or operation go into revenue service — and the proving and validation records are the proof that authorization was earned.
Does §135.145 apply to single-pilot aircraft?
Generally no. The proving requirements in §135.145(a) and (b) are written around two specific categories: an aircraft (other than a turbojet) for which two pilots are required by the chapter for operations under VFR, and a turbojet airplane. The validation trigger in §135.145(d)(1) is likewise tied to an aircraft for which two pilots are required for operations under VFR or a turbojet airplane. A piston single or light twin operated single-pilot that is not in either category does not trigger the (a)/(b)/(d)(1) proving and validation requirements on the basis of the aircraft type alone. Note, though, that the other §135.145(d) triggers are not about the aircraft at all — operations outside U.S. airspace, Class II navigation, and special performance or operational authorizations can require validation testing regardless of how many pilots the aircraft needs. As always, the Administrator makes the call, and the safest course is to ask your assigned FAA office before you assume an operation is exempt.
Can validation tests be completed without actually flying?
Sometimes, for validation tests specifically. Section 135.145(e) provides that validation tests must be accomplished by test methods acceptable to the Administrator, and that actual flights may not be required when an applicant can demonstrate competence and compliance with appropriate regulations without conducting a flight. That is a meaningful difference from proving tests, which are built around flying at least 25 hours. So a validation requirement attached to, for example, a special operational authorization may be satisfiable through a demonstration of capability acceptable to the FAA rather than a flight — but the method has to be one the Administrator accepts, and the determination is the FAA's. Section 135.145(f) also allows proving and validation tests to be conducted simultaneously when appropriate, and §135.145(g) allows the Administrator to authorize deviations from the section where special circumstances make full compliance unnecessary.
Does FileFlo run proving tests or file the OpSpecs authorization?
No. FileFlo is a compliance document intelligence platform — it classifies, indexes, version-tracks, and surfaces expirations on the records a proving or validation test generates and the records the aircraft carries: the test plan, the flight-time and approach logs, the FAA acceptance, the registration and airworthiness certificates, the maintenance status records, the training records, and the operations specifications revisions that follow a successful test. It does not plan or fly proving tests, schedule or perform the demonstration, communicate with your principal inspectors, or amend your operations specifications. Those belong to your director of operations, your check airmen and crews, and the FAA. What FileFlo does is keep the resulting record complete, current, and retrievable — so when an inspector asks for the proving file or the OpSpecs authorization behind a particular aircraft, it is one search away.
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FileFlo classifies and tracks the documents a proving or validation test runs on — the accepted test plan, the flight-time and approach logs, the FAA acceptance, the OpSpecs authorization, and the maintenance and training records the new type carries into service — then keeps every expiration on watch. AI document classification. 600+ document types. One-click audit binder for the FSDO. Starter at $89/mo, Professional at $299/mo.
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Continue your Part 135 / Part 91 / Part 145 compliance reading
Reviewed by Chad Griffith, Founder, FileFlo — compliance document intelligence. Last reviewed June 13, 2026. Regulatory citations verified against the Cornell Legal Information Institute eCFR (14 CFR §§135.145, 135.63, 119.5, and 119.51, and 49 U.S.C. §46301 as adjusted by 14 CFR §13.301) as of the publication date. Descriptions of FAA proving and validation practice and operations specifications conventions are an orientation to FAA process and guidance, not CFR — confirm specifics with your assigned FSDO and your own issued operations specifications.