Wow, I can't believe no one has responded to this. It was actually a significant part of the NPR story this evening on the travel re-start. They reported it would take up to 2 weeks to clear the backlog; the interviewer said that actually seemed kind of short to her, and it does to me as well.

They also said ticketed passengers get priority on scheduled flights (of course), and after that foreign visitors trying to get home would take precedence over (for example) British citizens trying to get out of London on holiday.