What condition must be met for the lateral separation to be valid in a controlled airspace setting?

The condition that must be met for lateral separation to be valid in a controlled airspace setting is that the aircraft must be beyond the protected airspace of each other. This means that the horizontal distance between aircraft must be sufficient to ensure they do not infringe upon each other’s safety zones, which are defined by regulatory standards. This lateral separation is crucial for preventing mid-air collisions and ensuring safe operations in controlled airspace, where multiple aircraft may be operating simultaneously.

Maintaining this separation allows air traffic controllers to effectively manage air traffic and provide safe guidance to pilots. Other factors like altitude, visual separation, and communication with ATC have their own importance in aviation safety, but they do not directly define the requirement for lateral separation to be considered valid.