A taxi driver is said to be in a critical condition after suffering a cardiac arrest before mounting the pavement and crashing into Heathrow's Terminal 5 building.
The accident, around 5.23am on Monday, closed one lane of the departure terminal's forecourt.
The ambulance service said the driver, thought to be in his 60s, suffered a cardiac arrest.
An ambulance service spokesman said the driver was taken to Hillingdon Hospital "as a priority".
The Independent quoted a hospital spokesman as saying the driver was now in a critical condition.
An investigation has been launched into the incident. A Heathrow worker told the Evening Standard: "We don't know what happened - we have cleared up the debris.
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"Luckily we don't think anyone apart from the driver was hurt. It could have been much worse."
The area where the incident happened was being repaired this afternoon, the newspaper reported.
Pictures taken in the aftermath of the crash showed a recovery vehicle hauling a Volkswagen people-carrier backwards away from the building.
The Volkswagen appeared to have rammed through a fence before smashing into a tall glass window pane on the side of the terminal.