Originally Posted by
newyorkgeorge
I was flying home last night on Flight #2391, the 777 DFW/MIA flight. Have taking the 777 MIA/DFW flights many times I know the crew works typically works the inbound #969 from MIA and then #2391 back, although usually different a/c (crew usually sits in DFW for a few hours). Yesterday the crew was late coming in from MIA so departure was pushed back from 4:45 to 5:30. When I arrived at the gate at 4:45 they were already boarding Group 2. When I asked a FA how they got off the inbound flight so quick, she said we are just the standby crew for boarding, your flight crew will arrive in about 15 minutes.
I've never seen a crew used just for boarding purposes. It allowed us to depart at 5:15, 15 minutes earlier and enabled some paxs to make their connections in MIA.

Reading this post, shows the nicety of keeping standby crews on hand to allow for late arrivals of the "real" crew. At major hubs does AA do this regularly. I've been on lots of flights where one (or more) crew members were arriving on an inbound, preventing timely boarding (hence late departure)--I've never seen standby crews being used.
[I assume these standbys are paid, even if not used.]