Join Date: Oct 2000
Location: Munich, Germany
Programs: LH HON, DL FO/MM, Marriott Lifetime Platinum, Accor Lifetime Platinum, Sixt Diamond
Posts: 6,174
Comparings this to any domestic flight is like comparing apples and oranges.
If they are cleared for departure, the flight is out of the US for any customs & immigrations related issues. Letting passengers deplane again would mean everybody going through customs & immigration again - something you don't want to do if you still want to get out the same night.