The crash at the Marana Regional Airport, about 21 miles northwest of Tucson, is the second fatal aviation mishap this month in Arizona.

Chatter over the airwaves has provided some clues about what happened in Arizona. A chief flight instructor who was in the air with a student that day heard the commotion over the radio: One plane was attempting a touch-and-go when another clipped its propeller while attempting to land.

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.