tom focus on. >> sreenivasan: brennan said u.s. authorities are working round the clock to prevent any holiday-season attack. so far, officials have said there is no specific, credible threat. one of the world's busiest international airports made slow progress today, getting back up to speed. snow and a deep freeze had all but paralyzed heathrow outside london since saturday. that in turn, roiled airline schedules around the globe. we have a report from chris choi of "independent television news." >> reporter: never have passengers been so relieved to escape the clutches of an airport, but the backlog that's turned terminals into squats continues. and tonight, we've learned police were called to the thai airways desk after angry scenes. >> i think just the frustration, i don't think anyone wants to take it out on the staff. i think it's the sheer frustration of nothing being done. >> it's just unbelievable that people are stuck up here and only the courtesy to just talk to somebody in a polite manner. >> reporter: the hibernation