Last month I had a PDX SEA flight that was delayed 1.5hrs due to ATC at SEA, after a while they started asking anyone in the gate area that was on one of the three delayed flights to SEA if they wanted to go to PAE on a flight that would leave in 20 mins. They even got those with checked bags moved over. he GA said it was a co-terminal and that is why they could offer the chance to change our flights.