The cause of an enormous blaze at a major London airport carpark that grounded flights and damaged 1500 vehicles has been discovered. 

London Luton Airport cancelled all flights until 3pm BST on Wednesday as firefighters battled the blaze in a multi-story carpark overnight - declaring a it “major incident”. 

Emergency responders from Bedfordshire Fire and Rescue identified a vehicle as the likely start of the blaze, which broke out on the third floor of the Terminal 2 carpark shortly before 9pm. 

“It’s believed to be diesel-powered at this stage, all subject to verification. And then that fire has quickly and rapidly spread,” Andrew Hopkinson, chief fire officer for Bedfordshire Fire and Rescue Service, told the Independent. 

The cause was not thought to be suspicious, with Hopkinson saying there was nothing to suggest it was anything other than an accident. 

The building saw “significant structural collapse” which damaged many of the 1900 vehicles stored in the Terminal 2 carpark. 

The fire was brought under control on Wednesday morning, but no passengers were able to travel until later that day, with the first service to take off being a delayed 1pm Ryanair service to Cork, which was delayed to 3.30pm. 

Up to 50,000 passengers are thought to have been affected by 273 flight suspensions and diversions to other UK Airports. 

One inbound flight from Egypt was diverted to Bristol - a distance of 200 kilometres. 

Passenger Jason Harris told the BBC he was offered a taxi by operator EasyJet back to Luton, and then had to order a second taxi home. 

Many diverted passengers diverted to alternate airports arranged to travel back to Luton, not knowing if they would be able to reclaim their parked vehicles - or if they had been damaged. 

The large international airport in north London is serviced by several low-cost carriers, and is a key hub for flights to Europe. 

London Luton Airport airport thanked passengers for their patience over a “difficult 24 hours”, and asked travellers to expect some additional delays and issues around parking availability. 

“While operations have resumed, some disruption is inevitable,” said the airport via X (formerly Twitter). 

Several airlines are warning there may be a long tail to disruption this week, telling passengers to expect delays. 

“While the airport has now partially re-opened, there are restrictions in place, which means that like other airlines, we are operating a significantly reduced flying programme for the remainder of the day, so some flights are unable to operate as planned,” said a statement from EasyJet. 

Ryanair and Wizzair said affected passengers would be contacted regarding delays.