More than 100 car owners have got their vehicles back after a private parking company at Gatwick Airport failed to return them, police said.
Several passengers reported booking their cars into the care of Gatwick First Parking and then not having their vehicles returned.
Sussex Police and Trading Standards found 120 vehicles at various sites in Sussex and Surrey.
Another 30 sets of keys have been found but the vehicles are still missing.
A police spokesman said Gatwick First Parking, which is not approved by the airport, appears to have ceased trading.
The keys to the 120 vehicles were found at the company's office in Surrey.
Sussex Police said they have no power to seize control of the keys of the cars, but had contacted landowners where the cars had been parked.
Landowners were then able to contact passengers to arrange for them to collect their cars.
Sgt Darren Taylor, of the Gatwick Policing Team, said: "It's essential that Gatwick Airport passengers use official on-airport parking, or companies registered with Gatwick's off-airport approved parking operators scheme only, to avoid this sort of thing from happening.
"We're carrying out further enquiries to locate the outstanding vehicles, and the owners of those vehicles will be contacted and kept up to date.
"Our priority is to find and return their vehicles to them as soon as we possibly can."