Airlines Replace Monitors After Air France Crash

While no cause has been established for the disaster, Derivry said the Pitot failures create "a web of presumptions, but only presumptions," that they could be a contributing factor.

The monitors had not yet been replaced on the A330 that was destroyed en route from Rio de Janeiro to Paris.

On Tuesday, the airline assured its pilots that none of its A330s or A340s would fly without at least two of the new instruments, and that all Air France A330s and A340s will have all three Pitots replaced by July. Brazil's air force said it is replacing them for the president's jet.

But some pilots said the planes should remain flyable even if Pitot tubes ice over in thunderstorms. And the European Aviation Safety Agency issued a precautionary safety bulletin Tuesday reminding operators about existing procedures to safely fly the aircraft even when air speed indicators malfunction.

"We are aware of issues with this in the past, but at no time were they classified as safety-critical," said Daniel Hoeltgen, the agency's spokesman.

About 70 airlines operate some 600 A330 planes similar to the doomed Air France jet, and two companies manufacture the Pitot monitors for them: France's Thales Group and Charlotte, North Carolina-based Goodrich Corp.