Maximum Cruise Speed: What is the value?

• A. 0.85 Mach
• B. 0.90 Mach
• C. 0.80 Mach
• D. 0.75 Mach

Answer: (A)

The concept being tested is the aircraft’s maximum cruise speed—the highest Mach number that can be safely sustained in cruise according to the aircraft’s certification and flight manual. This limit is set to protect the airframe, engines, and flight stability (buffet margins, structural loads, and propulsion performance) while still allowing efficient operation.

For the CRJ-550, the published maximum cruise speed is Mach 0.85. That value represents the upper bound you must not exceed in cruise because going faster could push you into conditions outside the certified limits. Speeds such as Mach 0.80 or Mach 0.75 are below that limit and can be used within normal operations, but they are not the maximum. Mach 0.90 would exceed the certified limit and isn’t permitted in normal cruise.