 -- Nearly 10 hours after firefighters extinguished the blaze at a Federal Aviation Administration Air Traffic Control Center in Aurora, Illinois, at least 1,669 flights have been canceled today in and out of the two Chicago airports, one of which is the world’s busiest.

As of 3:25 p.m. ET, there were 1,669 canceled flights that were to go in and out of O'Hare and Midway Airports today and 353 delayed flights.

The fire, thought to be started by a contract employee, started a day after Chicago Mayor Rahm Emanuel proudly proclaimed O'Hare as the world's busiest airport for the first time since 2004, according to the Federal Aviation Administration. More than 580,000 flights departed or landed at the airport from January to August.

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But there was little to celebrate today, as frustrated travelers shared photos of crowded airport terminals and endless lines through social media sites like Instagram and Twitter.