I don't know why the airlines don't just keep a fleet of small planes to shuttle crews back and forth in these situations.
Because it doesn't happen that often, and if it does happen they can easily move their crews around on scheduled flights. This got screwed up not because they needed to get the employees on the flight, it got screwed up because some idiot in charge decided to forcibly remove a paying passenger instead of offering a suitable amount of money to get some other passenger to give up their seat. There were a couple of other passengers that were willing to give up their seats but not for the amount offered, they tried to negotiate with the gate agent but the agent blew them off and called security to remove Dao. I'll bet United wishes they'd tossed a few hundred more bucks in the pot now.
