That controller has been suspended pending an investigation.
Reagan National is just seconds by air from the White House, the Capitol and many landmarks.
The two planes involved were an American Airlines flight from Miami and a United flight from Chicago. The pilots had to land on their own with no help from the tower.
Only one controller was on duty that night. That's apparently normal procedure at that time of day, but the nation's transportation secretary has changed that.
The pilots of the two planes were eventually able to land safely after contact with controllers at a regional Federal Aviation Administration facility 40 miles away.
Although the incident happened at Reagan National Airport, some air travelers at O'Hare wondered whether it could happen in Chicago.
"I hope it doesn't," said traveler Will Reese. "Now I have to be concerned about it."
"What's frightening is all the work the T.S.A. does and airports do to ensure the travelers stay safe. Then you have someone on the other side falling asleep when planes are landing," said traveler Thomas O'Connor.
The controller who fell asleep was a supervisor with 20 years' experience and has been suspended. Investigators say he was working his fourth consecutive overnight shift.
As authorities call for at least two staffers on the midnight shift, United States Senator Mark Kirk says the FAA needs to look into its existing procedures.
"There are two sets of issues. One: you can't have an unmanned control tower at any airport. Secondly, at National Airport within sight of the White House, you need more of the a-team. Having a controller asleep on the job should cost them their job immediately to send a signal to everyone else," said Kirk.
The controllers union has long opposed one person shifts.
On Thursday, officials added a second overnight controller at Reagan National Airport but declined to say if similar changes are needed at 29 other commercial airports with single controller shifts.
"This incident has given us cause to take a good look at this, and we're going to review this situation and make a decision," said Randy Babbitt of the Federal Aviation Administration.
A retired O'Hare controllersays many things could've gone wrong.
"Suppose there was a vehicle on the runway - and when you're landing at night you don't always necessarily see them coming in - it's hard to pick them out," said retired O'Hare air traffic controller Bob Richards.
After a 2006 Comair crash in Kentucky, the FAA staffed all airports with at least two controllers, but that policy was eventually relaxed.
Chicago attorney Michael Krzak of Clifford Law Offices represented Comair victims' families.
"You don't know if a controller that's there by himself is going to have a heart attack, is going to have food poisoning, is going to have to use the restroom," said Krzak.
Novice air traveler Crystal Shaulis just hopes she's safe.
"It's scary because this is my first flight by myself," Shaulis told ABC7.
According to airport sources, O'Hare's air traffic control towers are staffed during the day with a mininum of 15 controllers and in the evening as many as 17. The overnight shift reportedly has at least one supervisor and three controllers on duty.
While some say the incident raises serious questions about controller fatigue and airport safety, Professor Aaron Gellman of the Transportation Center at Northwestern University says the issue has more to do with merit than money.
"Are they really the people you want doing those jobs? Are they well qualified and do they have the temperament and the capaility of understanding the complexity?" said Gellman.