The latest theory about the Air France 447 disaster is that bad speed readings caused the Airbus's computer control systems to go haywire--and that, while rebooting the computers and flying on backup instruments, the pilots flew the plane so fast that it broke up in mid-air.

This theory has been given credence by another Airbus's systems going nuts in a similar situation last week, this time over the Pacific:

WSJ: A Northwest Airlines A330 flying from Hong Kong to Tokyo... ran into a situation which investigators believe may be a similar to what took place on the flight deck of the Air France jet.

The Northwest crew reported entering a storm in daylight and running into turbulence; in less than a minute their primary and standby airspeed indicators showed the plane had slowed dramatically. Other systems that automatically maintain speed and altitude also disengaged. "The master warning and master caution" indications flashed on the instrument panel, according to one crew member's written description, "and the sound of chirps and clicks (followed) letting us know these things were happening."

Things didn't return to normal for three minutes as the captain flew the aircraft out of the rain, according to information gathered by U.S. safety officials.

The scene inside Air France Flight 447 may have been more ominous from the beginning. The crew was flying at night and the storm they tried to traverse may have been more violent.

After the initial speed warnings, the Air France pilots are believed to have quickly lost the autopilot and automated throttle-controls, which are designed to instantly disengage when speed readings are suspect. Soon after, according to people familiar with the investigation, cockpit instruments showed a series of warnings about various other equipment failures and the crew apparently shut down or tried to reboot their primary and secondary computer systems.

It's not clear what happened next. But the pilots, perhaps distracted by wildly fluctuating airspeed indications, along with the cacophony of other cockpit warnings, could have allowed the jetliner to gain excessive speed that possibly tore off sections of the plane.

The aircraft could have accelerated and run into danger because faulty instruments convinced the Air France crew the twin-engine jet was traveling so slowly that it was close to stalling. That may have prompted them to rev up the engines or point the nose down to go faster.

These incidents, along with others, will likely increase concerns about the "fly-by-wire" planes built by Airbus and, soon, Boeing.

Hydraulic systems can break, too, of course--and have. But to a generation of folks reared on computers that crash constantly for no apparent reason (and resist most attempts to diagnose the problem), the concept of a "software glitch" blowing up their airplane has the potential to be particularly terrifying.