Originally Posted by
DawgmanOH
Yep, well aware UA has a larger presence. What I was trying to find is the criteria for getting a wheels up time and who assigns it? For example, is it granted based on gate availability (i.e. maybe no gate for the UA planes to get to) or is it granted as long as they can safely land? And does FAA grant it, the airport or the airline?
The FAA uses ration-by-schedule to allocate the slots in the delay program. So if there's 60 flights scheduled this hour, and the FAA thinks they can only handle 30 arrivals an hour, they'll spread those flights out evenly over the next 2 hours. Then all the flights in the next hour need to be allocated similarly over subsequent hours.
Once the airlines get their slots (including mainline gets to control their regional partner's slots), the airline is free to swap around flights as they see fit. They can prioritize small delays for large/longhaul aircraft and longer delays for small/shorthaul aircraft. They can move a bunch of flights up with swaps, pushing one flight to the end of the day, and then cancel that one flight. They can prioritize elite heavy flights, flights with crews facing timeout, etc etc.
So this ATL-ORD flight lost out with an EDCT 4 hours after the original scheduled departure time because UA prioritized other flights over it.