>> reporter: tonight, the faa investigating a fourth aviation incident in less than a month. at around 10:00 saturday evening, an american airlines airbus being towed at l.a.x. colliding with a moving passenger shuttle bus. the bus driver with his head bandaged, put in a wheelchair. two additional bus passengers and two airport workers also injured. the four were taken to the hospital for non-serious injuries. >> anyone who has ever watched out the window at l.a.x. is aware of the incredible complexity of the orchestration of buses and trucks and cars and airplanes, all having to stay clear of each other. this is something that has to be looked at. >> reporter: and last week in austin, a fedex cargo plane coming in to land when a southwest flight was cleared to take off from the same runway. disaster was averted when the fedex crew decided to break off the approach. last month at jfk an american airlines flight crossing an active runway as a delta flight accelerated down the same runway for takeoff. the delta flight aborting just in time. >> while at first glance, it's easy to say, well, the