One man, aged in his 40s, was taken to a west London hospital and has since died.
Passengers were evacuated from a plane after this morning's "serious accident". A second man was treated at the scene for minor injuries.
An employee of London's Heathrow Airport was killed in a "serious accident" between vehicles on the airfield on Wednesday.
In a post to Twitter the airport said the incident involved "two members of staff", adding: "An investigation is underway and we are working with the police".
The Health and Safety Executive was informed and officers from the Met's serious collision investigation unit were at the scene.More news: Three arrested in Hawks Gupta raid in Saxonwold
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"Our deepest condolences go to the family and friends affected by this accident". Heathrow Airport representatives said additional delays are not expected.
It also reported the condition of people involved with the, saying a man has been pronounced dead in a hospital while the other is in a stable condition with a broken shoulder.
A British Airways spokesman said: "We are deeply saddened by this tragic incident and are offering our full care and support to his family and colleagues". A post-mortem will be scheduled in due course.
The Met said it was investigating the incident but no arrests had been made.
Heathrow said the airfield remained open during the incident and it worked "to minimise disruption to passengers' journeys". Another 20 British Airways flights were delayed, affecting hundreds of travelers. "We are doing all we can to ensure they will be able to depart as soon as possible", she added.