Air France: Where Things Stand as Black Box Signals Fade

June 26, 2009— -- It's been nearly four weeks since Air France flight 447 crashed into the Atlantic Ocean enroute to Paris from Rio de Janeiro. Search teams are now racing against the clock to find the most vital clues to the crash -- the plane's black boxes -- before their signals fade.

At the same time, the National Transportation Safety Board this week is investigating two other incidents involving Airbus A330 planes like the one that crashed. The safety board wants to learn more about reported problems with airspeed and altitude information. It's known there were faulty airspeed readings on the Air France flight before the accident, and that's been a focus of the investigation.

Here's the latest on where things stand:

The bureau also said it would release its first factual report on what happened on July 2.

See ABC News photo gallery of the search effort here.

Watch ABC News Video on the Crash:
Air France Crash Questions Sensor Safety (June 9, 2009)
Search Intensifies for Black Boxes (June 8, 2009)
Plane Disappears Off Radar (June 1, 2009)

Read ABC News Stories on the Crash:
French Sub Joins Black Box Search (June 10, 2009)
Carriers Rush to Replace Speed Sensors (June 9, 2009)
Jet's Tail Could Lead to Answers (June 8, 2009)
Air France Official: 'We Can Fear the Worst' (June 1, 2009)

Accident investigators have said speed sensors malfunctioned on the flight, and the problem could have caused the plane to fly dangerously slow or fast. Last week, Pierre-Henri Gourgeon, Air France-KLM managing director, said, "We cannot, however, assume any link between the sensors and the causes of the accident." Meantime, airlines worldwide, including Delta, US Airways and United, are scrambling to replace speed sensors on a number of Airbus jets.

Airbus recommended replacing the speed sensor 17 months ago after reports that they'd malfunctioned or iced over, but it wasn't an urgent problem. On Monday, June 8, Airbus sent a note to its customers specifying that the Airbus A330 and A340 were "safe," even if still equipped with the older speed sensors. The sensors had not yet been changed on Air France Flight 447.

But it's too early to rule out terrorism entirely, officials have said. On June 5, French Defense Minister Herve Morin said there was "no element or lead that would allow to corroborate this, but the ongoing investigation never ruled out this because the main threat today against our democracies is terrorism."

A bomb threat on an Air France flight from South America to Paris fueled speculation about terrorism, but there is no evidence of a similar threat to the accident flight. The threatened May 27 flight from Buenos Aires to Paris was inspected before takeoff and was allowed to depart after investigators found nothing of concern.

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FAA Holds Regional Airline Safety Summit (June 15, 2009)
Capt. Sully Sullenberger Recounts Landing on Hudson River (June 9, 2009)
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The Black Holes of Plane Crashes (June 4, 2009)
Fear of Flying Causes Families to Split Flights (June 4, 2009)

ABC News' Lisa Stark, Christophe Schpoliansky, Zoe Magee, Ammu Kannampilly, Renata Araujo and The Associated Press contributed to this report.