longest war and survived so many close calls there. here again tonight, richard engel in kabul. >> reporter: at kabul international airport, time is running out. the u.s. and nato allies have just one week to pull out all their citizens and vulnerable afghans after the taliban today insisted they would semino extensions beyond august 31st or there would be consequences. the u.s. embassy today apparently feeling the strain issuing a final alert for american citizens to leave tonight or they would be on their own. then recalling it 30 minutes later. this is now an extremely busy air field. every few minutes, new planes are coming in and they are not just there united states. we've seen them from the u.k., qatar, civilian aircraft. this is a truly global air lift. the satellite images show the huge crowds trying to leave the airport.