thorough once-over before rejoining the fleet. that s after passengers aboard a southwest 737 watched a large hole rip over at 36,000 feet in the air on friday. a flight safety expert told me earlier today what likely happened. southwest operates aircraft in what s called a high-cycle, high-fatigue environment. they run up and down. in other words, the plane goes from ground to altitude, back down which is a pressurization cycle quite frequently, much more so than a lot of other airlines. what happens is we exercise that fuselage, it blows up, if you will with pressure and deflates when we are back on the ground, they tend to flex the metallurgy in the whole structure, which is normal stuff. no one was seriously hurt when the southwest flight made an emergency landing of on friday in arizona. inspectors say the external skin of the plane came apart at a rivet line. southwest cancelled is hundreds of flights yesterday to accommodate the inspections. in japan, rescuers ar