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121 fatalities

Helios Airways Flight 522 Crash (5B-DBY)

Grammatiko, GreeceFlight

On August 14, 2005, a Boeing 737-300 (registration 5B-DBY) operated by Helios Airways was involved in an aviation accident near Grammatiko, Greece in flight. 121 people were killed. Investigators recorded the probable cause as: The accident was caused by the flight crew's failure to recognize that the cabin pressurization mode selector was in the manual position, leading to hypoxia and incapacitation. This summary draws on records from the Bureau of Aircraft Accidents Archives (B3A); 8 related events involving the same aircraft type or operator are linked below.

Sourcesthe Bureau of Aircraft Accidents Archives (B3A)Primary report: the Air Accident Investigation and Aviation Safety Board of Greece (AAIASB)Updated 2026-09-03Data APIEditorial standards
Aircraft registered 5B-DBY
Aircraft registered 5B-DBY. Photo: CC BY-SA 3.0, via Wikimedia Commons

A Helios Airways Boeing 737-300 crashed in Greece on 14 August 2005 after the crew became incapacitated by hypoxia. All 121 people on board were killed.

Flight Details and Initial AnomaliesOn 14 August 2005, a Boeing 737-300 with registration 5B-DBY, operated by Helios Airways, departed Larnaca, Cyprus, at 06:07 for Prague, Czech Republic, via Athens, Greece. The aircraft was cleared to climb to flight level 340. During the climb through 16,000 feet, the Captain reported a take-off configuration warning and an equipment cooling system problem to the company Operations Centre. Communications regarding these issues continued until the aircraft climbed through 28,900 feet, after which the aircraft stopped responding to radio calls. At 18,200 feet, the passenger oxygen masks deployed in the cabin. The aircraft leveled off at flight level 340 and continued on its programmed route.

Probable cause

The accident was caused by the flight crew's failure to recognize that the cabin pressurization mode selector was in the manual position, leading to hypoxia and incapacitation. The aircraft then continued on autopilot until fuel depletion caused engine flameout and a crash into terrain.

Related events

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Frequently asked questions

What happened in the 14 Aug 2005 Boeing 737-300 accident near Grammatiko, Greece?

A Helios Airways Boeing 737-300 crashed in Greece on 14 August 2005 after the crew became incapacitated by hypoxia. All 121 people on board were killed.

Were there any fatalities in the 14 Aug 2005 Boeing 737-300 accident?

The accident was fatal, resulting in 121 fatalities.

What aircraft was involved and where did it happen?

The accident on 14 Aug 2005 involved a Boeing 737-300, registration 5B-DBY, operated by Helios Airways, at Grammatiko, Greece.

What was the probable cause of the accident?

The accident was caused by the flight crew's failure to recognize that the cabin pressurization mode selector was in the manual position, leading to hypoxia and incapacitation. The aircraft then continued on autopilot until fuel depletion caused engine flameout and a crash into terrain.

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