---
kind: "section"
citation: "14 C.F.R. § 135.321"
title: "14"
number: "135.321"
heading: "Applicability and terms used."
url: "https://uscodex.org/cfr/14/135.321"
---

# §135.321. Applicability and terms used.

- (a) Except as provided in [§ 135.3](/cfr/14/135.3.md), this subpart prescribes the requirements applicable to—
  - (1) A certificate holder under this part which contracts with, or otherwise arranges to use the services of a training center certificated under [part 142](/cfr/14/part142.md) to perform training, testing, and checking functions;
  - (2) Each certificate holder for establishing and maintaining an approved training program for crewmembers, check pilots and instructors, and other operations personnel employed or used by that certificate holder; and
  - (3) Each certificate holder for the qualification, approval, and use of aircraft simulators and flight training devices in the conduct of the program.
- (b) **For the purposes of this subpart, the following terms and definitions apply—**
  - (1) **Initial training.** The training required for crewmembers who have not qualified and served in the same capacity on an aircraft.
  - (2) **Transition training.** The training required for crewmembers who have qualified and served in the same capacity on another aircraft.
  - (3) **Upgrade training.** The training required for crewmembers who have qualified and served as second in command on a particular aircraft type, before they serve as pilot in command on that aircraft.
  - (4) **Differences training.** The training required for crewmembers who have qualified and served on a particular type aircraft, when the Administrator finds differences training is necessary before a crewmember serves in the same capacity on a particular variation of that aircraft.
  - (5) **Recurrent training.** The training required for crewmembers to remain adequately trained and currently proficient for each aircraft, crewmember position, and type of operation in which the crewmember serves.
  - (6) **In flight.** The maneuvers, procedures, or functions that must be conducted in the aircraft.
  - (7) **Training center.** An organization governed by the applicable requirements of [part 142](/cfr/14/part142.md) of this chapter that conducts training, testing, and checking under contract or other arrangement to certificate holders subject to the requirements of this part.
  - (8) **Requalification training.** The training required for crewmembers previously trained and qualified, but who have become unqualified due to not having met within the required period the—
    - (i) Recurrent pilot testing requirements of [§ 135.293](/cfr/14/135.293.md);
    - (ii) Instrument proficiency check requirements of [§ 135.297](/cfr/14/135.297.md); or
    - (iii) Line checks required by [§ 135.299](/cfr/14/135.299.md).

## Notes

### Amendments

[Docket 16097, 43 FR 46783, Oct. 10, 1978, as amended by Amdt. 121-250, 60 FR 65950, Dec. 20, 1995; Amdt. 135-63, 61 FR 34561, July 2, 1996; Amdt. 135-91, 68 FR 54588, Sept. 17, 2003; Docket FAA-2019-0360, Amdt. 135-145, 89 FR 51430, June 18, 2024]

### Authority

Authority: 49 U.S.C. 106(f), 40113, 41706, 44701-44702, 44705, 44709, 44711-44713, 44715-44717, 44722, 44730, 45101-45105; Pub. L. 112-95, 126 Stat. 58 (49 U.S.C. 44730).

### Source

Source: Docket 16097, 43 FR 46783, Oct. 10, 1978, unless otherwise noted.

### Amendments

[Docket 16097, 43 FR 46783, Oct. 10, 1978, as amended by Amdt. 121-250, 60 FR 65950, Dec. 20, 1995; Amdt. 135-63, 61 FR 34561, July 2, 1996; Amdt. 135-91, 68 FR 54588, Sept. 17, 2003; Docket FAA-2019-0360, Amdt. 135-145, 89 FR 51430, June 18, 2024]