---
kind: "section"
citation: "14 C.F.R. § 38.19"
title: "14"
number: "38.19"
heading: "Change criteria."
url: "https://uscodex.org/cfr/14/38.19"
---

# §38.19. Change criteria.

- (a) For an airplane that has been shown to comply with [§ 38.17](/cfr/14/38.17.md), any subsequent version of that airplane must demonstrate compliance with [§ 38.17](/cfr/14/38.17.md) if the subsequent version incorporates a modification that either increases:
  - (1) The maximum takeoff mass; or
  - (2) The fuel efficiency metric value by a percentage that is more than the following calculated thresholds.
    - (i) For airplanes with a MTOM greater than or equal to 5,700 kg, the threshold decreases linearly from 1.35 percent for an airplane with a MTOM of 5,700 kg to 0.75 percent for an airplane with a MTOM of 60,000 kg.
    - (ii) For airplanes with a MTOM greater than or equal to 60,000 kg, the threshold decreases linearly from 0.75 percent for an airplane with a MTOM of 60,000 kg to 0.70 percent for airplanes with a MTOM of 600,000 kg.
    - (iii) For airplanes with a MTOM greater than or equal to 600,000 kg, the threshold is 0.70 percent.
- (b) For an airplane that has been shown to comply with [§ 38.17](/cfr/14/38.17.md), and for any subsequent version of that airplane that incorporates modifications that do not increase the MTOM or the fuel efficiency metric value in excess of the levels shown in [paragraph (a)](#a) of this section, the fuel efficiency metric value of the modified airplane may be reported to be the same as the value prior to modification.
- (c) For an airplane that meets the criteria of § [38.1(a)(4)](/cfr/14/38.1.md?p=a-4) or [(5)](/cfr/14/38.1.md?p=a-5), on or after January 1, 2023, and before January 1, 2028, the airplane must demonstrate compliance with [§ 38.17](/cfr/14/38.17.md) if it incorporates any modification that increases the fuel efficiency metric value of the airplane prior to modification by more than 1.5 percent.

## Notes

### Authority

Authority: 42 U.S.C. 4321 et seq., 7572; 49 U.S.C. 106(g), 40113, 44701-44702, 44704; 49 CFR 1.83(c)

### Source

Source: Docket No. FAA-2022-0241, Amdt. No. 21-107, 89 FR 12654, Feb. 16, 2024, unless otherwise noted.