Concerns over safety in the aftermath of the EygptAir 767 crash in which 217 people died have prompted Boeing to halt delivery of 34 airliners across four model ranges.
Boeing stressed that the decision was not related to the accident. The Federal Aviation Authority confirmed it had not issued an airworthiness directive to the company nor does one appear imminent.
The problem was discovered after a laboratory test on a piece of cockpit shielding, which when exposed to flame failed to meet flammability requirements. The three layers from which it is formed turned out to have been improperly bonded.
A fault has also been discovered in the drip shield which prevents condensation from reaching cockpit wiring and instruments.
There are hundreds of Boeing 747s, 757s, 767s and 777s in operation which contain the offending drip shields. Boeing confirmed that all affected planes would soon be modified.