This day in history

34 Years ago today: On 10 SEP 1976 a British Airways Trident collided with an Inex Adria Dc-9 over Vrobec, killing 176 people.
Date:    10 SEP 1976
Time:    10:14
Type:    Hawker Siddeley HS-121 Trident 3B
Operator:    British Airways
Registration:    G-AWZT
C/n / msn:    2320
First flight:    1972
Total airframe hrs:    8627
Cycles:    6952
Engines:    3 Rolls Royce 512-5W Spey
Crew:    Fatalities: 9 / Occupants: 9
Passengers:    Fatalities: 54 / Occupants: 54
Total:    Fatalities: 63 / Occupants: 63
Collision casualties:    Fatalities: 113
Airplane damage:    Written off
Airplane fate:    Written off (damaged beyond repair)
Location:    near Vrbovec (Croatia) show on map
Phase:    En route (ENR)
Nature:    International Scheduled Passenger
Departure airport:    London-Heathrow Airport (LHR/EGLL), United Kingdom
Destination airport:    Istanbul-Yesilköy Airport (IST/LTBA), Turkey
Flightnumber:    475

Narrative:
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."