What happened
On the night of 31 August 1966, a non-scheduled flight operated by BY 105 departed from Luton, England, bound for Ljubljana, Yugoslavia. The aircraft was transporting 110 passengers and 7 crew members. During the flight, the crew maintained regular radio contact with the Zagreb Area Control Centre and later with Ljubljana Aerodrome Control.
As the aircraft approached the destination, the controller provided meteorological updates, noting calm winds, visibility of 5 kilometers, and the formation of shallow fog. The controller also provided pressure settings, specifically a QNH of 1011 mb and a QFE of 968 mb. The crew confirmed they were following instructions to descend to 4,500 feet and requested confirmation regarding the serviceability of the ILS, which the controller verified as operational.
While on the approach to runway 31, the crew requested radar assistance. The controller monitored the aircraft's position via radar, noting it was approximately 2 NM from touchdown. After observing the aircraft begin a rightward deviation, the controller attempted to provide a correction and inquired if the pilot was turning toward the Menges radio beacon. The crew did not respond to this inquiry. Radar contact was lost at 0047 hours local time on 1 September 1966. Shortly thereafter, smoke and fire were observed from the control tower.
Emergency responders located the wreckage in a wooded area approximately 2.8 km southeast of the runway 31 threshold. The impact and subsequent fire destroyed the aircraft. Of the 117 people on board, 98 fatalities occurred, while 19 individuals—one crew member and 18 passengers—were evacuated to a hospital.
Findings
The investigation concluded that the pilot-in-command failed to adjust the altimeter to the provided QFE of 968 mb. Consequently, the approach was flown approximately 1,250 feet below the required safety altitude, leading the aircraft into the treetops. While the co-pilot's altimeter was set to the QNH, he did not identify the low altitude because the dark, tree-covered terrain prevented him from recognizing visual landmarks.
The failure to perform required altimeter cross-checks as mandated by the operations manual meant the error remained undetected. The investigation noted that the calm weather and moonlight may have reduced the crew's concentration on strict procedural adherence, and the perceived slope of the runway further contributed to a distorted perception of the approach angle.