 It is firmly established only that the El Al flight, flying at FL180 (an altitude of approximately 18,000 feet above mean sea level), strayed off the Amber 10 airway into Bulgarian territory.Bypassing the town of Tran, the El Al plane traveled a total of over Bulgarian territory at a distance from the border it crossed, before being shot down.The aircraft's crossing of the Western Bulgarian border was registered by an observation post of the Bulgarian military near the town of Tran, and the Air Defence scrambled two MiG-15 jets with pilots Petrov (pair leader) and Sankiisky, by order of the Deputy Chief of Air Defense, Gen. Velitchko Georgiev.