Were the pilots distracted? Catching up on their sleep? Federal investigators struggled to determine what the crew of a Northwest Airlines jetliner were doing at 37,000 feet as theyand military jets scrambled 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.
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.
Meanwhile, police and FBI agents on the ground were preparing for the worst, and the Air National Guard put four fighter jets on strip alert - pilots in cockpit with engines running - in case the incident turned out to be more serious, reports CBS News correspondent David Martin.
With worries about terrorists still high, even after contact was re-established, air traffic controllers ordered the plane to execute two additional turns to confirm that the pilots were in fact controlling the aircraft, reports CBS News correspondent Wyatt Andrews.
"There's a number of procedures that air traffic control have employed after 9/11 to help identify that the plane is not under the control of terrorists," former NTSB managing director Peter Goelz told Andrews.
A report released by airport police Friday identified the pilot as Timothy B. Cheney and the first officer as Richard I. Cole. The report said the men were "cooperative, apologetic and appreciative" and volunteered to take preliminary breath tests that were 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.
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 cockpit voice recorder and flight data recorder arrived in Washington for examination Friday morning, an NTSB official told CBS News.
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. Even the bright city lights of Minneapolis should have clued them in that they'd reached their destination.
"It's is probably something you would say never would happen if this hadn't just happened," Voss said.
The pilots were finally alerted to their situation when a flight attendant called on an intercom from the cabin. Two pilots flying in the vicinity were also finally able to raise the Northwest pilots using a Denver traffic control radio frequency instead of the local Minneapolis frequency.
On the ground, police and FBI agents prepared for the worst.
"When the aircraft taxied to the gate I was able to see the two white males in the seats of the flight crew, both were wearing uniforms consistent with Delta flight crew," said a police report, signed by an Officer Starch. "When the aircraft had stopped, the male seated in the pilot seat turned, looked at me and gave me two thumbs up and shook his head indicating all was OK."
Air traffic controllers in Denver had been in contact with the pilots as they flew over the Rockies, FAA spokeswoman Laura Brown said. But as the plane got closer to Minneapolis, she said, "the Denver center tried to contact the flight but couldn't get anyone."
Denver controllers notified their counterparts in Minneapolis, who also tried to reach the crew without success, Brown said.
Officials suspect Flight 188's radio might still have been tuned to a frequency used by Denver controllers even though the plane had flown beyond their reach, said Church, the spokesman for the National Air Traffic Controllers Union. Controllers worked throughout the incident with the pilots of other planes, asking them to try to raise Flight 188 using the Denver frequency, he said.
Passenger Andrea Allmon told CBS News she was "horrified" the pilots weren't paying attention.
"Their job is to fly the plane. My job is to ride the plane," Allmon said. "They are supposed to fly the plane - it's unbelievable, unbelievable."
Another passenger, Lonnie Heidtke, said he didn't notice anything unusual before the landing except that the plane was late.
The flight attendants "did say there was a delay and we'd have to orbit or something to that effect before we got back. They really didn't say we overflew Minneapolis. ... They implied it was just a business-as-usual delay," said Heidtke, a consultant with a supercomputer consulting company based in Bloomington, Minn.
Once on the ground, the plane was met by police and FBI agents. Passengers retrieving their luggage from overhead bins were asked by flight attendants sit down, Heidtke said. An airport police officer and a couple other people came on board and stood at the cockpit door, talking to the pilots, he said.
"I did jokingly call my wife and say, 'This is the first time I've seen the police meet the plane. Maybe they're going to arrest the pilots for being so late.' Maybe I was right," Heidtke said.
In January 2008, two pilots for go! airlines fell asleep for at least 18 minutes during a midmorning flight from Honolulu to Hilo, Hawaii. The plane passed its destination and was heading out over open ocean before controllers raised the pilots. The captain was later diagnosed with sleep apnea.
FAA spokesman Tony Molinaro said in general, an unsafe condition created by a pilot could lead to the suspension of the person's pilot license and possibly a civil penalty.