While switching air space. the investigation has raised a lot of questions about how air traffic controllers communicate. david mulko takes a look at that story. >> reporter: cleared for takeoff. spoken hundreds of times a day. up in the control tower at hong kong international airport. as the plane climbs out, it's handed from the tow to the air traffic control center. responsible not just for the space around the airport, but for the entire region. each colored strip, each dat on the screen a piece of this delicate puzzle. >> she has to control the outbound traffic, the inbound traffic and t...