An exhausted operator could be behind today's commuter train derailment at Chicago's O'Hare International Airport. 

Sources close to the investigation say the operator was extremely tired and may have dozed off. 

She’d reportedly worked a lot of overtime in recent weeks and it was simply catching up to her. 

She apparently never hit the brakes once the train made it to O’Hare. 

More than 30 people were injured when the train jumped the tracks around 3:00 this morning.