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.

A midair collision involving two small planes in southern Arizona killed two people Wednesday morning, authorities said. Federal air-safety investigators said each plane had two people aboard when they collided at Marana Regional Airport on the outskirts of Tucson.

Tens of thousands of planes take off, land and perform touch-and-goes at the Marana Regional Airport in southern Arizona every year. Without an air traffic control tower, it's a calculated dance that requires communication by pilots.