14 CFR 25.601 : Aeronautics And Space (§ 1.1 To Parts 1311-1399) — (§ 1.1 To Parts 50-59) — Federal Aviation Administration, Department Of Transportation (§ 1.1 To Parts 50-59) — Aircraft (§ 21.1 To Parts 50-59) — Airworthiness Standards: Transport Category Airplanes (§ 25.1 To Appendix O To Part 25) — Design And Construction (§ 25.601 To § 25.899) — General (§ 25.601 To § 25.631) — General.

4 Aug 2016

The airplane may not have design features or details that experience has shown to be hazardous or unreliable. The suitability of each questionable design detail and part must be established by tests.

14 CFR 25.601