Four years after it was detected, the Israeli air force is still not fully sure how an irritating substance penetrated the cockpits of its Lockheed Martin F-16I "Sufa" strike aircraft.
When pilots first reported the irritation to their noses and eyes it was suspected that the problem had been caused by formaldehyde, a carcinogenic substance.
The air force's F-16I fleet was temporarily grounded until it became clear that this was not the substance in question. The aircraft were returned to service after a few days, with tests having continued in full co-operation with the type's US manufacturer.
The Israeli air force is still not fully sure how an irritating substance penetrated the cockpits of its Lockheed Martin F-16s
A source related to the ongoing effort to find the source of the problem said it is now clear the issue is a result of the combination between the "surroundings" of the Pratt & Whitney F100-229 engine and the software of the F-16I's air conditioning system.
The source of the irritant is believed to stem from fuel and engine exhaust fumes that find their way into the pilot's breathing system.
The source noted that this is a unique combination, as other air forces operating the same block of fighter have not detected a problem.
The Israeli air force has made a number of changes, including the installation of a special filter, and is continuing to monitor the situation. "The effort focuses now on a set of solutions that are expected to eliminate the problem completely," the source said.