Language & WorldHow it works
How thousands of aircraft manage not to collide at once.
Airspace is divided into sectors, each handled by one controller. On the ground, the tower directs take-off and landing; approach control takes over next, and an area control centre handles the cruise. At each sector boundary the aircraft is handed off by radio. The rule: at least 5 nautical miles apart laterally or 1,000 feet vertically. TCAS warns pilots too.
Useful: Circling in a holding pattern before landing is a safety buffer, not a malfunction.
Source: en.wikipedia.org