Keep in mind that's its very expensive for an aircraft to divert like this. AA had to charter buses at the last minute and then had to fly an empty aircraft from LAX to SNA.

If its not legal (think all the calculations that go into stopping an aircraft and then add extra margin of safety), then the pilot can't land. In that scenario, the dispatch folks are usually saying can't do it. Even if legal, the pilot can still say, it's too close of a call.

Lots of aircraft have run out of runway over the years ... no reason to take that chance.