Before modifying an FMC flight path, what is required for safety?

• A. ATC approval only.
• B. Both pilots must agree the new flight path is correct.
• C. Just the captain's approval.
• D. A ground check.

Answer: (B)

Cooperation and cross-check between the two pilots are essential whenever the flight path in the FMC is changed. The safety reason is that modifying the route affects the aircraft’s planned trajectory, potential conflicts with other traffic, terrain, weather, and any existing ATC clearances. When both pilots review and confirm the new path together, they share the responsibility for validating waypoints, altitudes, speeds, restrictions, and whether the change integrates properly with current clearances. This joint verification helps catch input mistakes, misinterpretations, or omissions before the aircraft actually flies the new path.

ATC approval is a separate process for routing and clearances, but it does not substitute for the crew’s mutual confirmation of the FMC change. Relying on just the captain’s approval or performing a ground check does not provide the same safety assurance as a coordinated two-person validation.