WASHINGTON — Were the pilots distracted? Catching up on their sleep? Federal investigators struggled to determine what the crew members of a Northwest Airlines jetliner were doing at 37,000 feet as they sped 150 miles past their Minneapolis destination and military jets prepared to chase them. Unfortunately, the cockpit voice recorder may not tell the tale.
A report released late Friday said the pilots passed Breathalyzer tests and were apologetic after Wednesday night's amazing odyssey. They said they had been having a heated discussion about airline policy. But aviation safety experts and other pilots were frankly skeptical they could have become so consumed with shop talk that they forgot to land an airplane carrying 144 passengers.
The most likely possibility, they said, is that the pilots simply fell asleep somewhere along their route from San Diego.
"It certainly is a plausible explanation," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Va.
One of the two pilots, first officer Richard I. Cole, said that wasn't the case.
"I can assure you none of us was asleep," Cole told ABC News. He declined to comment further except to say, "I am not doing very good."
New recorders retain as much as two hours of cockpit conversation and other noise, but the older model aboard Northwest's Flight 188 includes just the last 30 minutes — only the very end of Wednesday night's flight after the pilots realized their error over Wisconsin and were heading back to Minneapolis.
They had flown through the night with no response as air traffic controllers in two states and pilots of other planes over a wide swath of the mid-continent tried to get their attention by radio, data message and cell phone. On the ground, concerned officials alerted National Guard jets to go after the airliner from two locations, though none of the military planes got off the runway.
With worries about terrorists still high, even after contact was re-established, air traffic controllers asked the crew to prove who they were by executing turns.
"Controllers have a heightened sense of vigilance when we're not able to talk to an aircraft. That's the reality post-9/11," said Doug Church, a spokesman for the National Air Traffic Controllers Association.
A report released by airport police Friday identified Cole, of Salem Ore., and the flight's captain, Timothy B. Cheney, of Gig Harbor, Wash. The report said the men were "cooperative, apologetic and appreciative" and volunteered to take preliminary breath tests that registered zero for alcohol use. The report also said the lead flight attendant told police she was unaware of any incident during the flight.
The pilots, both temporarily suspended, are to be interviewed by NTSB investigators next week. The airline, acquired last year by Delta Air Lines, is also investigating. Messages left at both men's homes were not immediately returned.
The FAA said Friday that letters had been sent informing the pilots they are being investigated by the agency and it is possible their pilot's licenses could be suspended or revoked.
Investigators don't know whether the pilots may have fallen asleep, but National Transportation Safety Board spokesman Keith Holloway said Friday that fatigue and cockpit distraction will be looked into. The plane's flight recorders were brought to the board's Washington headquarters.
Voss, the Flight Safety Foundation president, said a special concern was that the many safety checks built into the aviation system to prevent incidents like this one — or to correct them quickly — apparently were ineffective until the very end. Not only couldn't air traffic controllers and other pilots raise the Northwest pilots for an hour, but the airline's dispatcher should have been trying to reach them as well. The three flight attendants onboard should have questioned why there were no preparations for landing being made. Brightly lit cockpit displays should have warned the pilots it was time to land. Despite cloudy conditions, the lights of Minneapolis should have clued them in that they'd reached their destination.
"It's probably something you would say never would happen if this hadn't just happened," Voss said.
Delta said Friday that it plans to give flight vouchers worth a few hundred dollars to each of the passengers.