# 14 CFR 39.15: ADs on a modified aircraft or part

> Yes, an AD still applies after the product has been changed. Modifying, altering or repairing the affected area does not take an aircraft or part out of an AD that names it.

Source: https://www.aerscheduler.com/regulations/39-15
Official text: https://www.ecfr.gov/current/title-14/section-39.15 (eCFR, current as of 2026-10-15; section last amended 2016-12-30)

## In plain English

- An AD applies to each product it identifies, even one that has been modified, altered or repaired in the area the AD covers.
- If the change makes the AD's actions impossible, the way out is an alternative method of compliance under 39.19, not ignoring the AD.

## Common questions

**My aircraft has an STC in the area the AD covers. Does the AD still apply?**

Yes, under 39.15. If the STC makes the AD's instructions unworkable, ask the FAA for an alternative method of compliance under 39.19.

## Official text of 14 CFR 39.15

Does an airworthiness directive apply if the product has been changed?.

Yes, an airworthiness directive applies to each product identified in the airworthiness directive, even if an individual product has been changed by modifying, altering, or repairing it in the area addressed by the airworthiness directive.

## Related

- [14 CFR 39.19: Alternative methods of compliance (AMOC)](https://www.aerscheduler.com/regulations/39-19.md)
- [14 CFR 39.7: Flying without complying with an AD](https://www.aerscheduler.com/regulations/39-7.md)
- [AD library: search FAA Airworthiness Directives](https://www.aerscheduler.com/airworthiness-directives)

AerScheduler lists the ADs that name each of your aircraft, records who decided each one, and tracks the repeat inspections that follow. [https://www.aerscheduler.com/features/inspections](https://www.aerscheduler.com/features/inspections)

_The plain-English summary is AerScheduler's reading of the rule, not legal advice. The official text above is the eCFR's, published by the Office of the Federal Register; the eCFR is the current text._