On May 3, 2020, a foaming incident took place after a fire extinguishing system was triggered. It happened in an aircraft hanger of British Airways at Heathrow Airport in London, UK. 

During that time, a Boeing 777-200ER aircraft of British Airways (Reg: G-YMMB), was parked in the hangar. 

Aeronews reported this by tweeting it 

Twitter Account: @AeronewsGlobal

Fire retardant foam that is mostly used in the maintenance for the aircraft hangers. Its capacity system can fill a large hanger in a period of short time in order to avoid the breakout of fire or any other damages in the hanger.

This particular foaming incident may appear to be small. But, repair costs are pretty high. Fire retardant foam, like the one shown in pictures, is highly burning to any aircraft that is in the hanger or nearby the surroundings.

The parts of the aircraft that are affected by the foam, like the main leading gear, are carefully analyzed and deeply cleaned by the experts. Precautionary measures will take in place in the future.