Originally Posted by PointWeasel

Keithguy is pretty close. In the busy summer months with cruise ship traffic, AS develops a YVR mini-hub and coordinates connecting pax travelling north to ANC/FAI and south from the same. Only adjacent transborder (US->US)gates E83 and E84 are used for this purpose and have a holding area where pax can sit until boarding their next flight and DO NOT have to undergo any Canada or US immigration/customs formalities. This is a fairly unique set-up and has been used for the past couple of years.