Safety regulators said Tuesday that American Airlines should figure out how it missed mechanical problems with a jet engine that caught fire during a 2007 flight, and then fix its maintenance program.
The safety officials also made several technical recommendations to the Federal Aviation Administration, including considering whether to require warning-system changes on jets like the one which caught fire.
An American Airlines plane with 143 people aboard was forced to make an emergency landing after an engine caught fire leaving St. Louis in September 2007. The plane landed safely, and there were no injuries.
At a public hearing last month, investigators for the National Transportation Safety Board said one engine on the American Airlines MD-82 had been difficult to start and maintenance crews replaced a starter valve six times in 10 days before the fire.
On Tuesday, the safety board recommended that American determine why it failed to catch the no-start problem with the jet and "discover the lack of compliance with company procedures." Then, the safety board said, the airline should make necessary changes to fix the problems.
Similar comments had been made last month at a public hearing into the incident.
Tim Smith, a spokesman for American, said the airline had already taken steps to fix the problems, including replacing air filters and start buttons on all its MD-80 series jets and giving additional training and directions to pilots and mechanics.
Testimony at the hearing indicated that mechanics contributed to the problems by failing to properly maintain a metal air filter and using the wrong tool, possibly a screwdriver, to manually start the troubled engine.
Smith said mechanics have been told specifically not to use screwdrivers on the restart button.
At the hearing, NTSB officials criticized the pilot and co-pilot for some actions, including interrupting an emergency checklist to tell passengers of the problem, which delayed shutting off fuel to the fire.
The fire damaged the plane's hydraulic system so badly that the rudder wasn't working and the nose landing gear failed to extend during the first landing try. A second attempt was successful, although the plane was heavily damaged.
Safety board members said last month that the fire could have had catastrophic results.
On Tuesday, the safety board made several recommendations to the FAA, which regulates airlines. These included determining whether changes should be made to a warning system in order to make it potentially more helpful to crew on all MD-80 series jets, and ensuring that pilots are trained to run checklists before engaging in "nonessential" tasks such as talking on the radio.
The board also recommended more guidance for pilots and flight attendants in how to handle emergency evacuations. In addition, it recommended that aircraft maker Boeing Co. tell airlines how often to replace air filters on air turbine starters — the filter that failed on the American jet.