Commuter Jet Crash in Kentucky Kills 49

Pat Smith, a member of Habitat for Humanity's international board of directors, had been on his way to join volunteers in Gulfport, Miss., where the organization is constructing 13 homes. The group has been building homes in the region since Hurricane Katrina hit a year ago. "Habitat for Humanity has lost a wonderful friend," the organization said in a statement.

The investigation began within hours after the crash, with federal safety authorities traveling to Kentucky from Washington.

Pilots who fly the same aircraft for other carriers said the Canadair Regional Jet needs at least 5,000 feet to take off fully loaded. "I'm questioning whether they could have gotten airborne" on a 3,400-foot runway, said safety expert John Cox, a pilot and former head of the Air Line Pilots Association. He said he had not flown the kind of aircraft involved in the crash -- but "I would expect you want something in the 4,000- to 5,000-foot range to get the plane airborne. You don't have it on that runway."

It was unclear why the Comair pilots used the smaller runway. Some experts said they could have been confused because the taxiway used to reach their intended runway first crosses the smaller runway. The predawn flight left when the airport was experiencing light rain, and instead of continuing down the taxiway, the pilots could have turned quickly onto the shorter runway, unaware it was the wrong one.

"If it was raining pretty good and visibility went down and they're looking not very far out but immediately out their windows, they may not have been able to see the signage to identify which runway they were on," said Gregg Feith, an aviation safety consultant and former NTSB accident investigator. "If they were using an airport diagram and had their head down, trying to figure this out and taxiing -- those momentary distractions take away from using other visual cues for validation."

The FAA said it recently sent an alert to pilots notifying them that Blue Grass Airport decided to stop maintaining the lights on the shorter runway after designating it for daytime use only. Officials did not know whether the lights on the smaller runway were operating on Sunday.

Safety experts said investigators will consider other possible causes of the crash, including whether the plane was overweight, the crew's flight schedule and whether it received adequate rest time, the crew's familiarity with the airport, aircraft-maintenance issues and weather, among other factors.

The NTSB said it began preliminary examinations of the flight data and cockpit voice recorders, also called the "black boxes," in Washington and found the cockpit voice recorder had 32 minutes of data. "We have a time-tested process that is methodical and extremely effective," said NTSB Chairman Mark V. Rosenker. "This is a horrible, horrible tragedy."

Investigators will still have to dig into why the crew made such a fatal error and why there weren't more survivors, said John Goglia, a former NTSB board member. "If that airplane came to rest where it did, usually you have a bit of time before the fire disables everybody," Goglia said. "Survival factors will be high on everyone's agenda."

The worst recent runway-related crash came on Oct. 31, 2000, when a Los Angeles-bound Singapore Airlines jumbo jet mistakenly went down a runway at Taiwan's Chiang Kai-shek International Airport that had been closed for repairs because of a recent typhoon. The resulting collision with construction equipment killed more than 80 people on board.

Some aviation officials consider the last 4 1/2 years to have been the safest period in U.S. aviation history. There has not been a major crash since Nov. 12, 2001, when American Airlines Flight 587 plummeted into a Queens, N.Y., neighborhood, killing 265 people, including five on the ground.

A number of smaller crashes have occurred since then, with most of them regional aircraft. Last December, a seaplane, a Grumman G-73 Turbo Mallard, operated by Chalk's Ocean Airways crashed off Miami Beach, killing 18 passengers and two crew members. In 2004, Corporate Airlines crew members who got little rest and were joking around in the cockpit failed to follow proper landing procedures in an accident that killed 11 of 13 passengers and two crew members in Kirksville, Mo. In 2003, a commuter plane crashed on takeoff at Charlotte-Douglas International Airport, killing all 19 passengers and both crew members.

Comair President Don Bornhorst said the airline had acquired the aircraft new in 2001. Maintenance has been up to date, including routine maintenance performed Sunday, Bornhorst said in a televised news conference. He said maintenance records have been "clean."

"There's nothing we're seeing that jumps out at us" in regard to maintenance issues, Bornhorst said. While he said he could give few details immediately because of the investigations into the accident, Bornhorst said there "was nothing of any weather challenge that stands out" as a possible cause.

Comair established a hotline for families and friends of the victims of the crash: 800-801-0088.

The carrier is based in the Cincinnati suburb of Erlanger, Ky. The twin-engine aircraft, a Bombardier Canadair CRJ-100, can carry 50 passengers, according to Delta's Web site.

FBI officials responded to the crash, but officials said their presence was a routine matter and that there was no evidence to suggest the crash was related to terrorism.

Goo reported from Washington. Staff writer Judy Sarasohn and researcher Rena Kirsch in Washington also contributed to this report.