The veteran controller at the Denver Air Route Traffic Control Center in Longmont was tested randomly 6-1/2 hours into his 8-hour shift July 5 and his blood-alcohol content was twice the legal limit, FAA sources told KMGH-TV in Denver.
The controller, who sources said was drunk while talking to pilots in the air, was immediately relieved of duty.
"The controller in question is not working air traffic. We are investigating the incident," said agency spokesman Mike Fergus, who could not confirm the blood-alcohol finding.
KMGH reports the man is a former official of his union, the National Air Traffic Controllers Association, and had more than 25 years on the job.
A relative said he has entered alcohol rehabilitation and the FAA has told him he can be reinstated if he completes his program, although it is unclear if he would ever again control live traffic.