And the aerospace giant will carry out changes to hundreds of planes already in service to correct a flaw in a cockpit shield that failed federal flame tests, said Jeff Hawk, director of aeroplane certification at Boeing's commercial division.

Thirty-four new 747, 757, 767 and 777 model planes will be delayed for "a few days" to ensure their drip shields, which keep moisture from seeping into the cockpit, are assembled according to the design approved by the US Federal Aviation Administration (FAA).

Unrelated to crash

"This is not related to any accident, incident or in-service event," Mr Hawk said.

The announcement was not related to the investigation into the cause of Sunday's crash of an EgyptAir Boeing 767-300ER passenger plane off the coast of Massachusetts, he said.

Although the faulty drip shield protected the cockpit from condensation it failed FAA flame tests, proving less resistant to fire than first thought.

"Condensation is going where it is supposed to go," Mr Hawk said.

"As assembled, the flammability characteristics are not as favourable as when the parts are properly assembled."

The drip shield is a hard, three-layer cap on the front of an aeroplane made of Kevlar or fibreglass and plastic. The version in service on the models in question was improperly bonded at Boeing's Spokane facility.

No immediate safety concerns

The drip shield flaw had not caused any problems on Boeing planes currently in service, he said.

"We do not see that there are any immediate safety issues with the drip shields currently in service."

Changes were being made to conform to FAA specifications.

Boeing has not yet estimated the cost of correcting the problem and declined to identify which customers will see their planes delayed.