CHICAGO_A deadly accident in which a Boeing 737 slid off the end of a snowy runway brought renewed demands Friday for buffer zones or other safety measures at hundreds of airports around the nation to give pilots a wider margin for error.
In Thursday night's tragedy at Midway Airport, a Southwest Airlines jet making a landing plowed through a fence and into a street, killing a 6-year-old boy in a car. Ten other people, most of them on the ground, were injured.
The National Transportation Safety Board said the cause of the accident was still under investigation, and the plane's voice and data recorders were sent to Washington for analysis. But much of the attention focused on the 6,500-foot runway.
Like nearly 300 other U.S. commercial airports, Midway lacks 1,000-foot buffer zones at the ends of its runways. Midway, a compact one mile square, was built in 1923 during the propeller era and has shorter runways than most major airports, with no room to extend them because it is hemmed in by houses and businesses.
Safety experts say such airports can guard against accidents by instead using beds of crushable concrete that can slow an aircraft if it slides off the end of a runway.
The concrete beds - called Engineered Material Arresting Systems, or EMAS - are in place at the end of 18 runways at 14 airports. They have stopped three dangerous overruns three times since May 1999 at Kennedy Airport in New York.
"Certainly Midway airport officials should have already been trying to come up with something similar to this," said Jim Hall, NTSB chairman from 1993 to 2001. "There's really no margin for error at the end of that runway."
Hall said the lack of a 1,000-foot overrun area and the absence of an EMAS system would probably be a key focus of the investigation.
"The bottom line is you have an increasing frequency of flights on a runway with an inadequate margin for error," he said. "It's a tragedy that did not have to occur."
Chicago Department of Aviation spokeswoman Wendy Abrams could not immediately say whether an arresting system had been considered at Midway.
Though the airport had about 7 inches of snow, aviation officials said conditions at the time were acceptable. And the plane did not appear to have any maintenance problems and had undergone a service check Wednesday in Phoenix, Southwest chief executive Gary Kelly said.
Southwest said the 59-year-old captain has been with the airline for more than 10 years, and the 35-year-old first officer who has flown with Southwest for 2 1/2 years. It was the first fatal crash in Southwest's 35-year history.
NTSB member Ellen Engleman Conners said the crew mentioned no problems with the aircraft before the landing.
Air traffic controllers had rated the braking condition of the runway at the time of accident as "fair" for most of the pavement and "poor" at the end, Conners said.
Investigators have not yet determined the exact spot where the plane touched down because it continued to snow after the accident.
"We can't say X marks the spot physically, but we will be able to determine that through a simulation," she said.
The plane hit the fence 32 seconds after it touched down. The jet's ground speed was 152 mph as it landed. It hit the fence at about 46 mph, Conners said.
Earlier, Conners stressed that a variety of factors need to be looked at before any cause is determined, including questions about the crew's performance, how the aircraft handled and air traffic control.
"Often, the first guess is not correct," Conners said. "So, we're not going to guess. We're going to focus on facts and science and data."
The plane may be moved out of the street and into a hangar Saturday, and the streets and runway may reopen by Sunday, Conners said. Interviews with the pilot, flight attendants and a witness were also planned for Saturday, she said.
A recently passed federal law seeks to encourage more airports to build EMAS systems or extend their runway barriers by requiring them to do one or the other by 2015. There are 284 such airports with neither feature, according to the FAA.
Southwest chief executive Gary Kelly said that the plane had recently had a maintenance check and showed no signs of problems.
Nearly 300 U.S. commercial airports lack 1,000-foot end-of-runway margin that the government considers adequate for safety.
Two packed passenger jets came within 1,000 feet (305 meters) of colliding last August at the same airport where a Southwest Airlines jet slid off a runway in December, killing a 6-year-old boy.
Studies by the city and the FAA in recent years determined that there is not enough room at the end of Midway's airstrips to install beds of crushable concrete that can slow an aircraft if it slides...