Airplanes: Turbine engine powered: En route limitations: Two engines inoperative

This regulation sets en route performance requirements for Part 121 turbine-powered airplanes when two engines fail simultaneously. The specific requirements depend on the aircraft's certification date, but all versions offer two compliance options:

Option 1: Stay within 90 minutes flying time (all engines operating at cruise power) of a suitable airport throughout the route.

Option 2: Operate at a weight that allows the airplane to reach a suitable airport after losing two engines, maintaining required terrain clearance using the net flight path data from the Airplane Flight Manual.

The terrain clearance requirements vary by certification date—older aircraft (pre-1958) need 1,000 feet above terrain or 5,000 feet minimum, while newer aircraft (post-1959) need 2,000 feet clearance. The newest category also requires arriving at the diversion airport at least 1,500 feet above the field with fuel for 15 additional minutes of cruise flight. This ensures multi-engine jets can safely reach an airport even after catastrophic dual-engine failure.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*