In air traffic control, a calculated time to depart after the meter fix in order to cross the vertex at the actual calculated time. This time reflects any descent speed adjustment and any applicable time that must be absorbed prior to crossing the meter fix. The vertex is the last fix on the arrival segment and is normally at the outer marker of the runway in use. However, it may be the actual threshold or another suitable common point on the approach path for the particular runway.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved