The controller thought it was a prank and dismissed the emergency call, according to recordings obtained by KUSA-TV (http://on9news.tv/HkWYhP ).
The United Express plane from Peoria, Ill., was evacuated Tuesday after landing at Denver International Airport. An FAA report said firefighters extinguished a fire in the instrument panel.
Controllers apparently realized the mistake when the pilot made another emergency call saying the plane had already landed and was evacuating on the runway. It was only then that fire trucks responded.
One of the 21 passengers was taken to the hospital.
A transcript of the recording shows that the controller apparently misunderstood the call letters of the airliner. According to KUSA-TV, a voice from the cockpit, either the co-pilot or pilot, is heard saying, "Emergency, smoke in the cockpit, roll trucks please" as the plane was coming in for a landing.
A controller in the tower responds, asking, "Who was that?"
The voice responded "5912" - the flight number that air controllers were tracking.
After some confusion, the controller responds about 10 seconds later, asking: "United 12, what's your position?"
After no response, more time elapsed before the controller says, "Did you hear that? I know that's BS. I know it is." Controllers said they were not aware of a United Flight 12.
Aviation analysts and a former pilot said Friday the first response from a controller should be to clear the decks of other aircraft after a pilot declares an emergency and treat the call as authentic.
Sid McGuirk, who teaches traffic management at Embry-Riddle Aeronautical University in Daytona Beach, Fla., said pilots are in control when there is an emergency and failure by controllers to respond would be a major violation of procedure that could result in discipline or retraining.
"They have to assume it's a real emergency, whether it's a Cessna or a 747 jumbo jet. If it later turns out to be a spoof, it's a federal crime," McGuirk said.
William Voss, president of the Flight Safety Foundation in Alexandria, Va., said pilots who declare an emergency are busy dealing with the problem, and it's easy to create confusion.
He said radios with airline frequencies are easily available and have been misused to report false emergencies.
The National Transportation Safety Board said the investigation has been turned over to the FAA, which said it would comment later Friday. The airline refused comment.
The union representing air traffic controllers did not return phone calls seeking reaction.
Katie Pribyl, a former United Express pilot, said she'd never heard of an air traffic controller not taking a request for an emergency landing seriously, but she said she also never heard of someone faking an emergency landing request.
"In my experience as a regional jet pilot, controllers normally took reported malfunctions very seriously," Pribyl said. "One of their first questions is usually, are you declaring an emergency?"
