An airport worker at Heathrow was killed this morning in a crash between two vehicles operating on the airfield.
The deceased, aged in his 40s, was taken to a west London hospital but could not be saved, the Metropolitan Police said.
"We treated two patients - both men".
A spokesman for Scotland Yard said: "Police were called at 6.06am on Wednesday, February 14, following a collision between two airport vehicles on the taxiway at Heathrow Airport". We await formal identification.
The second man involved in the incident was treated for a shoulder injury which has been described as "non-life threatening".
At least 20 British Airways flights from Terminal 5 were delayed and passengers were ordered to leave an aircraft which was unable to take off because of the incident.
It added that the deceased man has yet to be formally identified, but his next of kin had been informed.
The London Ambulance Service also attended, with one other man left with a suspected broken shoulder.
A post-mortem will be scheduled in due course.
The Health and Safety Executive were informed of the incident, but no arrests were made.
A BA spokeswoman said: "We are deeply saddened by this tragic incident and are offering our full care and support to his family and colleagues".
A British Airways engineer, in his 40s, suffered a cardiac arrest at the scene and was pronounced dead in hospital after paramedics battled to save him. British Airways confirmed that "inaccessible stands" were causing delays to departures.
It said the airfield remained open and staff were working to keep the disruption to a minimum.