It could take a number of years for taxpayers to see a return on public investment in Prestwick Airport, Scotland's infrastructure secretary has told MSPs.
The Scottish government took the loss-making airport into public hands last year from New Zealand owner Infratil.
Infrastructure Secretary Nicola Sturgeon said ministers had invested £5m in the airport to date.
She added that more investment would be required.
Prestwick, which was sold for £1 to the Scottish government on 22 November last year, had a pre-tax loss of £9.77m in the final full year of its ownership by Infratil.
It was a sharp worsening of its financial position, after a £2.3m pre-tax loss in the year to March 2012.
Ms Sturgeon told Holyrood's Infrastructure Committee it was possible to get a return on the taxpayers' money and find a private sector buyer, but added MSPs should keep an open mind on possible alternatives.
She said: "Cardiff Airport is owned by the Welsh government so we shouldn't close our minds to anything around the future potential model that you might want for an airport.
"The government owns a number of airports, obviously very small or regional airports, but it remains my working assumption that we will seek to return Prestwick to the private sector.
"That is certainly what I said was my preferred option, I wouldn't depart from that today.
"I don't think that's something that's going to happen in the short term. That will only be possible once we get the airport to a point where it is a viable proposition for a private sector operator to take over.
"Once we have come through this transitionary period I may be able to put a timescale on when that will be possible."
She added: "I'm not suggesting it will be easy. This will take a lot of time, effort and investment. We are potentially in it for the long haul.
"We compiled a business plan that indicated that the business can produce a return on the investment we will make.
"We acknowledge that it will be challenging and that it will take a number of years."
Ms Sturgeon also argued that the airport had already produced "positive" results since it was sold, with a 4% increase in passenger numbers and 3% increase in freight volume.
"There's a long way to go but nevertheless there is positive progress which we are pleased to report," she added.
It is estimated the airport supports 1,400 local jobs, and is worth £60m to the Scottish economy.