Final answer:
Air traffic safety for commercial airliners is maintained by the Federal Aviation Administration through strict regulations that define minimum horizontal and vertical distances between aircraft, ensuring collision-free flight paths.
Step-by-step explanation:
Commercial airliners are able to fly safely without colliding due to the rigorous air traffic control regulations put in place by the Federal Aviation Administration (FAA). To prevent in-flight collisions, the FAA requires that each plane must keep a minimum distance of five miles horizontally from another plane at the same altitude. Additionally, there is a vertical separation of 2,000 feet required between planes flying above and below each other, which is reduced to 1,000 feet if they are flying at altitudes lower than 29,000 feet. These safety protocols are designed to ensure that despite the high volume of air traffic, each aircraft has a prescribed space that it can safely occupy without risking collision.