Flights have now resumed but thousands of passengers have had their flights and travel plans halted or disrupted. The Fire and Rescue Service advised the inferno has caused the building to suffer a "significant structural collapse" and it may need to be completely demolished.
The fire started at about 20:45 BST and whilst there have been no serious injuries were reported a small number of firefighters have been treated for the effects of smoke inhalation.
Andy Hopkinson, Bedfordshire's chief fire officer, said firefighters faced a "severe and rapidly spreading fire" upon arrival, with the blaze "ultimately spread to multiple floors". He confirmed the service had "no intelligence than to suggest it was anything other than an accidental fire". He also stated the car park had as many as 1,500 vehicles in it at the time - with around 1,200 thought to be damaged.
According to an airport spokesperson, passengers arriving by car could now use the long and mid-stay car parks, while a temporary drop-off was established at the mid-stay car park. A temporary ramp was being installed to enable undamaged vehicles to be removed.