Statuts:	Enquête Officielle
Date:	10 SEP 1976
Heure:	10:14
Type/Sous-type:	McDonnell Douglas DC-9-31
Compagnie:	Inex Adria Aviopromet
Immatriculation:	YU-AJR
Numéro de série:	47649/741
Année de Fabrication:	1976
Heures de vol:	1345
Cycles:	990
Moteurs:	2 Pratt & Whitney JT8D-9A
Equipage:	victimes: 5 / à bord: 5
Passagers:	victimes: 108 / à bord: 108
Total:	victimes: 113 / à bord: 113
Victime de la collision:	victimes: 63
Dégats de l'appareil:	Détruit
Conséquences:	Written off (damaged beyond repair)
Lieu de l'accident:	près de Vrbovec (Croatie)
Phase de vol:	En vol (ENR)
Nature:	Charter International
Aéroport de départ:	Split Airport (SPU/LDSP), Croatie
Aéroport de destination:	Köln/Bonn Airport (CGN/EDDK), Allemagne
Numéro de vol:	550

Détails:
Flight BA475 (a HS-121 Trident) took from London-Heathrow at 08:32 GMT for a flight to Istanbul. About 1½ hours later, the aircraft approached the ZAG VOR beacon on airway UB5 at FL330 (10000m), heading 116° (speed 905km/h).
At the same time the Inex Adria DC-9-31 also approached the ZAG VOR, but flew airway UB9, climbing from FL260 to FL350. The DC-9 had taken off from Split at 09:48 GMT for a flight to Köln. At 10:14:14 the DC-9 captain radioed that they were climbing through FL325. According to ATC data the Flight BA475 was approaching ZAG VOR at FL335 (FL330 actually). Zagreb ATC asked (in Serbo-Croatian) the Inex flight to maintain their present altitude. At 10:14:38 the crew of flight JP550 replied (also in Serbo-Croatian) that they where maintaining FL330. Three seconds afterwards the outer five meters of the DC-9's left wing cut through the Trident's cockpit.
Due to the sudden decompression, the forward part of the Trident's fuselage disintegrated. The remaining part of the fuselage struck the ground tail-first and slid some 4-5m. to the left.
With it's left wing torn off, the DC-9 tumbled down and hit the ground right-wing first.

CAUSES OF THE ACCIDENT: "1) Direct cause of the accident was the struck of the DC-9 wing into the middle side of the TRIDENT THREE fuselage which occurred at the height of 33.000 feet above Zagreb VOR so that both aircraft became uncontrollable and fell on the ground.; 2) Improper ATC operation; 3) Non-compliance with regulations on continuous listening to the appropriate radio frequency of ATC and non-performance of look-out duty from the cockpits of either aircraft."

Sources:
» Air Disasters / Stanley Stewart
» Collision course / by Tony Brkic
Sample newspaper article from Newspaperarchive.com