The McDonnell Douglas DC-9-32 with 115 passengers and 5 crew on board descended, under Instrument Meteorological Conditions (IMC), below defined Minimum Descent Altitude (MDA) during the final approach to Prague Ruzyně Airport RWY 25, entered a gorge above Vltava river, and was unable to outclimb the rising terrain.

[3] The DC-9 was operated by Inex-Adria Aviopromet on a morning flight from Tivat to Prague with mostly Czechoslovakian tourists returning home from vacations on the Adriatic sea.

Captain Miodrag Marović (40) and First Officer Rade Popov (49) had an uneventful flight with clear weather, until they entered a published landing procedure above PR non-directional beacon (NDB).

Since ATC never mentioned approach lights to be out of service, this message from the crew reveals that mental load started to build up caused by the uneasiness with the situation at the airport.

In addition, while executing a non-standard right turn the crew positioned the aircraft to the south (left) of the published glide path for the final approach.

This horizontal deviation from the glide path continued to increase and at the place of the impact it was approximately 0.7 nmi (1.3 km; 0.81 mi).

During this communication the crew continued to descend below the altitude approved by the ATC and deviate horizontally from the glide path, flying directly towards a Suchdol’s gorge, cut by the Vltava river, and well below the airport's elevation.

Moreover, some sources[4][5] cited the official report that the CVR stopped recording some 15 minutes before the crash due to a short magnetic tape, so there is no data regarding cockpit communication in this critical part of the flight.

It is unknown: The crash ensued due to the crew descending the aircraft below published MDA and below altitude approved by the ATC.

They based this theory on statements that passengers near the cockpit, shortly before the impact, have heard the pilot announcing visual contact with the runway and starting to land.

However, bearing in mind that ILS and PAR were inoperative, it can happen that the crew was intensively looking out for a visual contact and thus missed to monitor the aircraft's altimeters and correlate read altitude to the ATC's instruction and airport's elevation.

The official report states that, during the inspection of the cockpit wreckage, it was found that "Both radio compasses on board the aircraft were set to only one beacon - PR".

Returning to the previous consideration that the crew was under stress and overwhelmed mentally due to inoperative ILS and PAR, it is highly likely that they were rather focused on looking for an outside visual contact than on instruments.

This standpoint is supported by Ladislav Keller, then Czechoslovakian civil pilot and air accident expert, who stated that the insufficient setting of the radio compasses indicated that the crew did not prepare well for landing, did not cooperate properly, and missed to monitor the instruments during the final approach.

Keller said: "If the crew stopped descending at decision height (Wiki author's comment: term Decision Height is used for a precision approach, while Minimum Descent Altitude term is used for a non-precision approach, which was flown by JP450), there would probably be no accident because the plane would fly about 90 meters above the runway threshold.