Alaska Airlines is grounding up to 18 Boeing MD-80 airliners for inspections of a part implicated in last January's crash that killed 88 people, the company said Thursday.
The airline reported to the Federal Aviation Administration that the tool used to check jackscrews may have produced incorrect readings. The jackscrew assembly consists of a nut that rides up and down a screw as it turns to lift and lower the stabilizer.
There are no indications of problems, the FAA said in a statement. But the agency is alerting other airlines using MD-80 planes - as well as DC-9 jets, which are also affected - to check their planes.
Alaska Airlines Flight 261 plunged into the ocean off Southern California on a flight from Mexico to San Francisco on Jan. 31. All 88 people aboard the plane, an MD-83 - an MD-80 variant - died.
A criminal investigation into the crash began focusing on a mechanic's decision not to replace a jackscrew assembly that was wearing out. The jackscrew had been tested repeatedly and found to be nearly worn out, but it was put back into service after a second crew retested it a few days later. Two Alaska Airlines mechanics insisted in an interview with The Seattle Times that they were not at fault.
The tool in question measures the amount of space between the thread on the jackscrew and the nut that holds it in place.
The airline's tests, conducted in the course of the National Transportation Safety Board investigation of the fatal crash, indicated that "endplay" measurement could vary. According to the MD-80 maintenance manual, airlines can measure jackscrew "endplay" using a tool made by the aircraft manufacturer or an equivalent substitute.
While Alaska owns tools made by the manufacturer, it also uses several that were made in its own machine shop. In side-by-side testing by the airline, the measurement using either tool produced the same results, the airline said. However, the airline found that the measurements could vary if its own tool was improperly positioned.
The airline's own tool was used to measure the jackscrew on Flight 261, airline President Bill Ayer told a news conference Thursday night.
"It is up to the U.S. Attorney's Office and the NTSB to determine if this tool is a problem in their investigation," he said.
On the performance of the two tools, he said, "We really got the same results but we found that the results could vary if the Alaska-made tool is incorrectly positioned."
Still, Ayer declared the MD-80s to be safe, adding, "There's no more inspected airplane in the world than the MD-80, especially the Alaska MD-80s."
Alaska, which has 500 departures daily, has a fleet of 92 planes, 34 of which are MD-80s.
The inspections resulted in about 20 flight cancellations Thursday night with an unspecified number of additional cancellations expected today, airline spokesman Greg Witter said.
The airline hoped to complete the inspections by late today, but service disruptions were expected to last at least through Saturday and possibly through the weekend.
Ayer said it was a common practice among airlines to make their own maintenance tools.
The airline verified that the manufacturer's tool was used to measure the jackscrews on 16 of its 34 MD-80s, so Alaska decided to reinspect the remaining 18 planes.
In June, the FAA announced that Alaska Airlines had made sufficient improvements to continue doing maintenance on its planes. Previously, the agency had threatened to strip the airline of the right to do maintenance - a step that could have eventually grounded all its planes - unless its programs were improved.