Do more U.S. airports need control towers? That's one of the questions that has arisen following a midair collision at an airport in southern Arizona last week.

In recent weeks, four major air disasters have occurred in North America. An American Airlines plane arriving at Ronald Reagan Washington National Airport interrupted its landing and made a turn on instructions from an air traffic controller to avoid getting too close to another aircraft taking off from the same runway,

An American Airlines flight was forced to abort its landing at Ronald Reagan Washington National Airport on Tuesday (February 25) to avoid another aircraft departing from the same runway. The incident involved American Flight 2246,