NTSB probes incident involving Northwest Airbus

Federal safety officials are investigating two reports of Airbus A330 planes experiencing airspeed and altitude malfunctions. One involves a Northwest Airlines plane.

The aircraft are the same type as the Air France plane that crashed into the North Atlantic on May 31 after sending out low airspeed messages. All 228 aboard died.

Now, federal safety investigators are looking into a TAM Airlines flight that experienced a loss of speed and altitude information.

They're also reviewing a possibly similar incident on a Northwest flight between Hong Kong and Tokyo. Both planes landed safely.

Northwest, which is now owned by Delta Air Lines, operates 32 A330 jets, mostly on international routes. Delta says it is cooperating with the safety investigation, and following Airbus recommendations to replace speed monitors on all of its A330s.

Air France Flight 447 came down in the mid-Atlantic on May 31 after running into thunderstorms en route from Rio de Janeiro to Paris.

The cause of the crash is unclear. Without the black boxes to help explain what went wrong, the crash investigation has focused on a flurry of automated messages sent by the airliner minutes before it lost contact.

One suggests that external speed sensors may have iced over, destabilizing the plane's control systems.

The automated messages were not alarm calls and no distress call was picked up from the plane.

Air France has replaced the speed sensors, called pitot tubes, on all its A330 and A340 aircraft, under pressure from pilots who feared a link to the accident.

The two incidents could provide important clues to what caused the Air France crash or they could turn out to have no relationship to it, said former NTSB board member John Goglia.

"You just don't know yet," Goglia said, "but they would really be remiss if they didn't explore these possibilities."

If Flight 447 also experienced a failure of the computer system that supplies key data like airspeed and altitude, Goglia said, that could explain the crash because when that happens "everything in the cockpit goes screwy - you have nothing to rely on."

"You speed up, you slow down. You go up, you go down. You have no reference," he said.

The NTSB is a party to the Air France investigation because the plane's engines and some of its cockpit navigation and communications systems came from U.S. manufacturers.

(The Associated Press contributed to this report)