The station serving the airport is two miles from the terminal building
A shuttle bus linking Cardiff Airport with its nearest railway station may be withdrawn at the end of next month.
Airport managers say they can no longer afford the £100,000 for the service, which started in 2005 following the opening of a new station at Rhoose.
The Vale of Glamorgan council said it was disappointed but a taxi firm was interested in providing an alternative for the two-mile service.
A rail watchdog said more regular trains might make it more popular.
The Welsh Assembly Government said it would work with all parties to see if the two-mile bus link could be saved.
The shuttle bus started after a £17m line carrying direct trains between Cardiff and Bridgend opened in 2005.
The airport said it cost more than £100,000 a year to run but carried fewer than than 1,000 passengers a week.
It said funding would end on 31 May.
A spokeswoman said: "We are disappointed that we have to do so as we fully support public transport.
"However, as a private company it is not viable to continue funding the service which does not affect airport passenger numbers.
"We look to work with both the assembly government and council on an alternative solution."
The shuttle bus currently meets all trains to Rhoose Cardiff International Airport station.
Trains run every hour from Monday to Saturday and every two hours on Sundays.
'For them to decide'
The Vale of Glamorgan council said it had been told of the withdrawal and felt the decision may reflect the "difficult economic conditions facing the country."
Cabinet member for transport Jeffrey James said: "It is a pity that this service is to be withdrawn, especially as the rail service is set to move to half hourly from 2014.
"I have already had an expression of interest from a taxi firm who is considering a possibility for filling the gap left by the bus being removed".
Simon Pickering, manager of the rail watchdog Passenger Focus in Wales said passengers would be disappointed by the news.
"Part of the problem with the current rail link service is that trains on the Vale of Glamorgan line are currently only hourly, and this relatively low frequency is likely to be deterring potential passengers from using the service to access the airport," he said.
"There are aspirations to make the train service half-hourly, which would help make the rail link a more attractive option.
"Hopefully, funding can be found in the interim to maintain the shuttle service so that it can take advantage of the plans for an enhanced train service."
An assembly government spokesperson said it was aware the airport was considering withdrawing the service.
"We will be working with them and the local authority to explore how we can work together to keep the service running," said a spokesperson.
"This service was funded by the airport operator and not Welsh Assembly Government. It is for them to decide if they wish to fund the service."
Airport management, meanwhile, said they were "most encouraged" at the prospect of a better bus link between Cardiff city centre and the terminal, which it is hoped will start in the autumn.