Yes, 3 hrs. for domestic flights for aircraft over 30 PAX and 4 hrs for international flights. But I think that is excessive as well & should be cut back to one Hr. & 2 Hrs. The most I ever sat on a tarmac was about 45 minutes in icy conditions...... ( fortunately I was in an aircraft when sitting on the tarmac
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I would agree that 3 hours is too long. It may have been before the legislation, but I remember landing at ORD in a thunderstorm, pulling up to the gate and stopping, then waiting for about 2 hours because they closed due to lightning. I could see people in the terminal. I could see the jet bridge. But no one was allowed to put the blocks on the plane or operate the jet bridge. If you ever wanted to see 200 people grumbling and cursing, that was the place...