Generally, required separation is 5 (nautical) miles or 1000 feet in altitude. There are some exceptions like taking off or landing on parallel runways. ATC wil

Generally, required separation is 5 (nautical) miles or 1000 feet in altitude. There are some exceptions like taking off or landing on parallel runways. ATC will ensure the separation, and on large airliners, the TCAS[1] system will alert pilots if something goes horribly wrong and aircraft get too close together. [1] https://en.wikipedia.org/wiki/Traffic_collision_avoidance_system https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...