On August 24, 2008, Iran Aseman Airlines Flight 6895 was only minutes into its journey from Bishkek, Kyrgyzstan, to Tehran, Iran, when a relatively routine technical problem triggered a chain of decisions that ended in one of Kyrgyzstan’s deadliest aviation disasters.

The Boeing 737-219 Advanced, registered EX-009, was operated by Kyrgyz airline Itek Air on behalf of Iran Aseman Airlines. There were 90 people aboard—85 passengers and five crew members. At about 8:30 p.m. local time, the aircraft departed Manas International Airport. Around seven minutes later, the crew reported a problem with cabin pressurization and decided to return to Manas.

The aircraft had climbed to approximately 3,000 metres when the crew told air traffic control about the problem. Investigators later determined that the forward left passenger door had not sealed correctly, probably because of a jammed door seal. This prevented the cabin from pressurizing normally.

Although the problem required the aircraft to return, investigators concluded that the loss of pressurization did not require an immediate emergency landing using a visual approach. An instrument approach could have been used instead.

The crew nevertheless elected to make a visual approach. It was already dark, but weather conditions were generally favourable.

As the Boeing approached Manas, the pilots realized that the aircraft was too high and too fast to make the intended landing. About 3.3 nautical miles from the airport reference point, the captain decided to perform a 360-degree turn in an attempt to lose altitude and speed before continuing toward the runway.

That turn became the critical moment of the flight.

While the aircraft was manoeuvring, the crew failed to maintain adequate control of its altitude and did not maintain the required visual references. The Boeing descended below the minimum altitude for the visual approach.

The situation was particularly dangerous because the aircraft was operating at night…