An interesting set of replies from the UK contingent on who has or should have priority.
The published guidelines suggest (training excepted) that it is broadly first come first serve with ATC flexing this to get the most capacity out of the system. Many places seem to do this. The comments from (some of) those that seem to be pilots and ATCOs suggest some places may have an undocumented Commercial First priority (and some airlines may think they should be first).
I personally think the based flag carrier should have priority over all other movements, except low fuel emergencies for competitors that have been holding to allow the Main User to stay on time (particularly up-start long haired competitors who should stay in music)
