[nuconvert]

It's possible that Phoenix airport is not equipped to handle this sort of emergency, and that's why they called it back. Also, we don't know how far into the flight this was. A bomb can have a timer..........better to get the plane back as fast as possible.

[CyberAnt]

I think you might be right about PHX not having as much sophisticated equipment as Midway, but also it may have a lot to do with how far the plane was from either airport. Had the plane been halfway to either airport, they could have chosen Omaha or another midpoint.