The wrong-airport landing by Southwest Airlines, the second incident in two months by US carriers, is heightening regulators' concerns that pilots are missing obvious visual and instrument cues while failing to check one another's work.
Lack of monitoring has been identified as an issue in the July 6 crash of an Asiana Airlines plane in San Francisco that killed three. An Atlas Air Worldwide Holdings jumbo- jet freighter used a municipal airport instead of McConnell Air Force Base on Nov. 20 in Wichita, Kansas.
Pilots of the Southwest Boeing 737-700 that landed after dark January 12 on a Branson, Missouri runway would have had multiple indications that they weren't at their intended destination seven miles away. They had to slam on the brakes to avoid going over an embankment at the end of a strip barely half the length of the one at their intended destination.
"It's a matter of a flight crew letting its guard down," Earl Weener, a member of the US National Transportation Safety Board who isn't involved in the Branson probe, said Monday in an interview at the North American International Auto Show in Detroit. "It's not unusual. I wish it were."
The NTSB and US Federal Aviation Administration are investigating the Branson incident. The pilots, who have been with Southwest for 26 years between them, were suspended with pay, according to the airline.
The safety board cited pilots' failure to monitor their instruments and flight path in the crash of a commuter flight by Pinnacle Airlines Corp's former Colgan unit on February 12, 2009. The crash killed 49 on the plane and a man on the ground.
Similar issues are under review in the Asiana crash, according to an NTSB hearing on the accident in December. Pilots didn't notice that the plane was flying too slow to stay aloft until seconds before it struck a seawall short of the runway at San Francisco International Airport, according to NTSB records.
Modern airliners are equipped with GPS guidance systems and computers programmed to find commercial airports. Even paper charts would have provided clues the Southwest pilots were approaching the wrong airport.
While both runways in Branson are headed southeast, they are 20 degrees off from each other.
The runway used by the Southwest pilots wasn't equipped with the colour-coded lights pilots use to tell whether they are high or low on approach, according to AirNav.com. Branson Airport has the lighting system.
Scientists who study human error have a term for why pilots sometimes press on in spite of clues that they shouldn't. It's called "confirmation bias," Patrick Veillette, a Park City, Utah, commercial pilot who has taught aviation safety, said in an interview.
Pilots descending on a dark night may spot an airport and instinctively head toward it, Veillette said. "If the runway is sort of the same direction you're expecting to land on, it's real easy to get fixated on that," he said.
"We seek out information that confirms our decision. We're not very good at noticing the cues saying, no, this isn't right," he said.
Pilots missing signs of trouble was identified as an issue in the 2002 charter plane crash that killed Senator Paul Wellstone, a Minnesota Democrat, and in a crash that year of a FedEx Corp. Boeing 727 in Tallahassee, Florida, according to a July 17 presentation by NTSB member Robert Sumwalt.
"It must become accepted that monitoring is a core skill," Sumwalt said, according to the NTSB's website.
Sumwalt is helping lead a study on the issue sponsored by the Alexandria, Virginia-based Flight Safety Foundation.
Investigators will want to know what the Southwest pilots discussed before attempting the landing in Branson and whether they tried to verify they were at the correct airport, Kevin Hiatt, president of the foundation, said in an interview.
"There is a lot of instrumentation there to indicate where they are," Hiatt said. "But how effective were they in using it?"
Flight 4013 from Chicago carried 124 passengers and five crew members, said Brad Hawkins, a spokesman for Dallas-based Southwest.
It landed shortly after sundown on the runway at M. Graham Clark Downtown Airport in Branson, which is 1,139 metres. The strip at their intended destination, Branson Airport, is 7,140 feet, according to the AirNav.com airport information website.
After an abrupt stop that flung passengers forward in their seats, and the cabin filled with the odour of burning rubber from the tires, a pilot acknowledged what had happened over the public address system, Scott Schieffer, a passenger, said in an interview.
"Ladies and gentleman, I am sorry, but we landed at the wrong airport," the pilot said, according to Schieffer, a Dallas tax and estate planning attorney.
The plane stopped within 200 feet of a rocky embankment that plunges toward a highway, he said.
The plane left the Branson county airport after it was inspected by Southwest crews, the airline said in a statement.