According to reports, the ice fault that cause a British Airways Boeing 777 to crash at Heathrow Airport in 2008 wasn’t covered by safety requirements. The crashing plane barely missed running into nearby buildings and the perimeter road, and the fault that caused it wasn’t covered by aviation safety requirements at the time.

The British Airways flight was carrying 136 passengers when it lost power, and the cabin crew were only aware of the engine trouble about 43 seconds before touchdown. Only 34 of the passengers and 12 crew suffered minor injuries. Most of these were to their necks and back, while one passenger’s leg was broken.

The jet had lost power due to a restricted flow of fuel to both its engines, according to Air Accident Investigation Branch. The investigation concluded that the crash on January 17, 2008 was most likely the cause of ice buildup in the plane’s fuel system. It is believed that ice formed from water that naturally occurs in the fuel when fuel temperatures are in a sticky range, causing ice crystals to develop.

At the time of the crash-landing safety regulations didn’t take this phenomenon into account, because the risk was unknown. They knew from 1950s research that ice could form in fuel systems from trapped or dissolved water, but they didn’t think it could restrict the flow of the fuel. So the Air Accident Investigation Branch ruled that the jet’s fuel oil heat exchanger was susceptible to restriction where there’s a high concentration of snow present while the temperature of the fuel is below -10°C (14°F).