Three German tourists say they have become unintentional vehicle thieves through a quirk of backpacker culture.

The tourists said they thought they were allowed to take a van left at Christchurch Airport with the keys in the driver's door as they had been told that backpackers sometimes left vehicles they could not sell at airports for other backpackers to take.

They spotted the van in what they said was a non-rental area of the airport car park and took it for a few days, but they were later arrested for unlawfully taking a rental van.

They were held in custody and appeared in the Christchurch District Court on Friday. They pleaded guilty to charges of unlawfully taking the $10,000 Lucky Rentals campervan on Tuesday.

The tourists were Hans Lorenz Steinfurth, 20, Friedrich Wiesbach, 21, both of Radebeul, and Isabelle Caroline Manna, 21, of Stephanskirchen.

They appeared in the dock together before Judge Noel Walsh, who was told the case needed to be dealt with on Friday because the tourists were continuing their journey.

Diversion for first offenders was not available at such short notice, and no restorative justice meeting could be held in the time available.

The judge bailed the three at the request of duty lawyer Michael Knowles to allow them to go to a bank and get the money they owed the rental van company.

They would have to return to the courthouse with the money in two hours, they were told.

Police prosecutor Sergeant Kathy Pomfrett told the court the rental van was dropped off at the airport car park by its previous hirer at 7.30am on Tuesday, and the keys were left in the driver's door.

The Germans went to the car park three hours later and looked around for a vehicle they could take and eventually headed off in the van.

Once they paid $602 to the court, as reparation to the rental van company, they were convicted and discharged and allowed to leave.

They had to wait at court while police informed the rental company that the money had been paid and they could retrieve their belongings, which were still in the van.

The tourists apologised for the theft, and Steinfurth said outside the court that they did not know it was a rental van.

They had been told by other travellers in Australia about backpackers leaving cars with the keys in them at airports when they could not sell them.

They planned to use the van for a couple of days and would then have returned it to the airport and left the keys, he said.

Manna said they

had not realised it was a rental because it was not parked in the area for rentals.

They plan to leave New Zealand on May 4.