PARIS — Air France pilots have asked French crash investigators for details of the airline’s past problems with the speed sensors suspected of being a factor in the crash of Air France Flight 447.

The Airbus A330 plane came down in the Atlantic Ocean on June 1 after running into thunderstorms en route from Rio de Janeiro to Paris. All 228 people aboard were killed, and the cause of the crash remains unclear.

The pilot’s union SPAF said in a letter Tuesday to France’s air accident investigation agency BEA and to the French civil aviation agency that past problems with the sensors, called Pitot tubes, constitute “serious incidents” that require both agencies to open technical investigations.

The union asked both agencies to give it information from those investigations.

Officials at the agencies couldn’t be reached for comment today.

SPAF president Gerard Arnoux said if, as he suspects, the agencies haven’t opened investigations yet into these Pitot tube incidents, then they are breaking their own rules.

“We accuse them of not taking the necessary measures,” Arnoux said.

BEA last week issued its preliminary report into the crash, finding that problems with the plane’s Pitot tubes were one of several factors in the crash. It said the plane hit the ocean intact and belly first at a high rate of speed.

“It is an element but not the cause,” BEA investigator Alain Bouillard said of the speed sensors.

In another letter Tuesday, the SPAF pilots’ union accused the European Aviation Safety Agency of not forcing Airbus to make modifications to its aircrafts’ speed sensors, saying such changes could have prevented Flight 447’s loss of control.

Problematic speed sensors on Airbus A330-200 jets have been the focus of intense speculation since the crash. An automatic message sent prior to the crash indicated the plane was receiving incorrect speed information from the external monitoring instruments, which could destabilize the plane’s control systems. Experts have suggested those external instruments might have iced over.

Today, two ships slowly continued to troll the Atlantic Ocean hundreds of miles off the northeastern coast of Brazil, towing two U.S. Navy black box pinger locators, said U.S. Army Lt. Col. Lorenzo Harris, part of the American team helping to oversee the search. No signals from the plane’s black boxes have been heard.

BEA says the search for the flight data and cockpit voice recorders will continue until Friday. The boxes are believed to be in very deep water, and their signal beacons began to fade more than a week ago.

French and Brazilian workers have also collected large amounts of Flight 447 debris and 50 bodies from the ocean to examine. Brazil lowered the body count to 50 after discovering one body was counted twice.

Brazil has led the search effort while France is leading the crash investigation.

Representatives from five of Air France’s pilots unions, meanwhile, met Tuesday with Air France managers for the first time since the BEA findings.

“We didn’t learn anything new,” said Francois Hamant, vice president of the Alter union.

It was the third such meeting since the crash. He said a fourth meeting was promised, but no date has been set.