El Al flight LY402 was a scheduled service from London, U.K. to Tel Aviv, Israel with en route stops at Paris, France and Vienna, Austria. The Constellation took off from Vienna at 02:53 for the last leg of the flight. The flight proceeded normally until over Yugoslavia. The airplane was following airway Amber 10 at FL180. The flight strayed off the airway and the crew misidentified the Skopje NDB, at which point the flight changed the heading to 142 degrees. This put the plane on a course to the Yugoslav/Bulgarian border. After straying into Bulgarian airspace, the flight was attacked by two Bulgarian MiG-15 fighter aircraft. The Constellation began a descent and was attacked for a second time at an altitude of 8000 feet. The airplane was now on fire as it descended for an emergency landing. After approximately five minutes a third attack took place at an altitude of about 2000 feet. As a result of this last attack, the aircraft broke up in mid-air. The Constellation had strayed off course because of an incorrect radio compass indication due to the effects of thunderstorm activity in the area. PROBABLE CAUSE: “The aircraft sustained a hit or hits which caused loss of pressurization and a fire in the heater compartment. The aircraft broke up in mid-air due to explosion caused by bullets hitting the right wing and probably the left wing together with a projectile or projectiles of large calibre in the rear end of the fuselage.”