I too was on UA 975 GVA-IAD yesterday and got caught in the "lockdown" standing in a long, crowded queue in the no-man's land between Customs/Immigration and security re-screening. The line between the snaky barricades just stopped moving.

The public address system was not used to inform us of what was happening, but a man in coat-and-tie (not the TSA uniform) eventually made a short and very hard to hear announcement from the side of the queue that "a passenger had breeched security" and that no passenger screenings would occur until that passenger was found in the airport. Also, don't worry because no flights will be leaving.

Although it was cool outside, the entire Customs/Immigration area and especially the area leading to security was very hot and humid. Bad enough if you have a place to sit, but harder if all you can do is stand or maybe sit on the floor. A couple of older people in the line were close to keeling over -- one very hard working young TSA guy took a lot of trouble to run and bring chairs and water for them and try to help them out. Kudos to him -- no kudos to the rest of TSA and Dulles airport for trapping upwards of 150 people in a closely confined space with poor ventilation, little information, and in the midst of a supposedly impending pandemic. There was a big fan (busy recycling hot air) and an outside door nearby -- maybe someone from TSA could have opened the door and used the fan to blow fresh air inside?

I think the problem with the premise (or outright lie) that "no flight are leaving" is that while it may be true that no flights leave during the lockdown, many people get backed up in queues during the freeze and those queues don't all unfreeze at the same rate. Apparently, flights are free to leave as soon as the problem is resolved and if they are close to pushback, then they may do so whether or not passengers are left behind. It did seem that TSA tried their best to clear the queue through security quickly after screenings resumed. Judging by the huge queue I observed at passenger services later, there were more than a few left behind.

In my own case, my connecting flight -- UA140 to LAS -- was delayed by 2.5 hours by an apparently unrelated problem (the aircraft was late in arriving) so I did not misconnect despite the lockdown. No explanation or apology was offered by United for this delay. In fact the existence of this delay was only mentioned in passing by the flight deck crew.

Question I have:

What happens if the problem that caused the lockdown can't be resolved in an hour or two?

What happens to arriving flights during a lockdown? Put in the penalty box? Diverted?

Anybody know why UA140 was delayed?