Plain English Meaning

Speed restrictions that only go down or stay the same as you move along the route — they never go back up. Once you've slowed to a given speed at one fix, the next fix won't ask you to be faster.

Full Definition

A sequence of speed reductions along a procedure in which each successive speed restriction is equal to or lower than the one before it, never increasing as the aircraft progresses along the path. In VNAV path construction, monotonic decelerations ensure the aircraft can continuously slow down through the procedure without ever being asked to speed back up between fixes.

Context Anchor

Seen in Vertical Navigation planning, especially when describing how a descent path is built from cruise flight toward approach and landing speeds.