What criteria must be met for both aircraft to report before discontinuing vertical separation?

For both aircraft to report before discontinuing vertical separation, it is crucial that both have reported passing a shared waypoint. This ensures that both aircraft are established on their respective flight paths and have a known positional reference, which is key for maintaining safe separation. By confirming that they have passed the same waypoint, air traffic controllers can have a clear understanding of their distances from that point and manage their vertical separation accordingly.

This criterion provides assurance that both aircraft are not only on converging flight paths but also that their altitudes are appropriately managed and coordinated. Having both aircraft report this waypoint before discontinuing vertical separation enhances safety by reducing the risk of unintended proximity, given that they are effectively at the same location in relation to their flight routes.

While the other criteria mentioned may also imply proximity or status in the flight profile, they do not specifically ensure the required spatial awareness and confirmed positioning necessary to safely discontinue vertical separation. For example, if both are on final approach but not at the same waypoint, they may still be on different paths leading to a potential conflict. Similarly, being in level flight or one being at a higher altitude does not guarantee the safety margin needed for maintaining vertical separation between the two aircraft. The necessity of reporting a shared waypoint therefore stands out as the