What happened
On January 6, 2003, a Jak 40 aircraft, registration EW 88161, operating a scheduled flight from Minsk to Prague, experienced an in-flight incident while cruising at FL 240. At approximately 09:35 UTC, the crew initially reported smoke within the cockpit. This report was subsequently corrected to indicate that the right-hand cockpit windshield had sustained a crack in its inner glass layer.
Following the discovery, the crew activated the 7700 emergency code while over Polish airspace and requested a descent to a safer altitude of FL 120. Although Warsaw ACC offered an alternative landing at Wroclaw airport, the commander elected to continue the flight to Prague at FL 120. As the aircraft entered Czech airspace, the crew descended further to FL 100 under instructions from Prague ACC. Due to the initial report of smoke, two Czech Air Force MiG 21MF interceptors were scrambled to visually monitor the aircraft from the rear hemisphere. After confirming the situation, the military escort was released at 10:03 UTC.
The aircraft landed safely at Prague airport at 10:15 UTC. There were no injuries to the crew or passengers.
The investigation
The ÚZPLN investigation established that the perceived smoke in the cockpit was not caused by fire, but was actually the result of condensation forming due to the breach in the inner layer of the windshield. The investigation also confirmed that the aircraft's pre-flight inspections had been completed correctly and that all crew members were properly qualified for the operation of the aircraft type.