Desperate travellers reportedly walked along the busy M4 motorway with their suitcases in a bid to make their flights from Heathrow, amid a major traffic jam blocking the route.
Some drivers have complained about being stuck for over an hour and a half following the incident.
Traffic was badly affected in the area surrounding the airport in West London, reported My London.
One witness in the area said: "People walking along hard shoulder with suitcases it’s lethal."
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Despite rumours there was some kind of protest causing the delays, a spokesperson for Heathrow Airport said it's been caused by a broken down bus blocking one of the tunnels.
The spokesperson said: “Our colleagues responded to a broken down bus earlier today which caused temporary congestion in the central terminal area tunnel. The vehicle has now been removed and traffic is flowing freely again through the tunnel.”
As well as the bus blocking traffic, the barriers at the short stay car park remained closed, according to people at the scene.
Susan and her husband David, who were meant to be on the long drive back to Durham, were stuck for two hours.
They told MyLondon: "We tried to ring the number but that took us 40 minutes to get through.
"The young lady was as much use as a chocolate fire guard.
"She told us the payment barriers weren’t working. Her advice was to get out the car park but that’s what I was ringing about it."
David continued: "It should be automated. Lack of staff, lack of communication. Normally we get the train but we were trying it out. We’ll never take the car again. Nor would we would use Heathrow.
"It cost us £77 to be held hostage for two hours."
The Met Police said police had been aware of the broken down bus in West Bore shortly before 11.30am.
Officers had also been informed that some passengers were attempting to walk down the carriageway towards the airport, a spokesperson said.
Officers attended and the pedestrians were put on other onward transport to the airport.
The roads were reopened at shortly after midday.
