London City airport has been warned by three airlines that they could pull out if new owners raise charges.

The airport has attracted interest from five potential buyers as owners Global Infrastructure Partners seeks to sell it for £2 billion.

British Airways has already raised concerns about the price tag and the potential for airline charges to go up, and they have now been joined by CityJet and Flybe.

City A.M. reports that an investigation commissioned by BA and CityJet has found fees are likely to be raised if the airport is sold for the £2 billion asking price.

“This brings into question the long-term sustainability of airline operations at London City airport,” CityJet executive chairman Pat Byrne said.

A deadline for bids has been set for this Friday, with Asia’s richest man, Li Ka-Shing, reported to be in the running .

BA, CityJet and Flybe account for 70% of the passengers that use the east London airport.

BA told City A.M.: “Any potential new owner for London City should be left in no doubt that British Airways can move flights elsewhere if it ramps up airport charges to fund its investment.”