Prestwick Airport is being put up for sale by the Scottish government.
The airport was taken into public ownership six years ago after it was threatened with closure following heavy losses.
Transport Scotland said an advert would be placed in the Official Journal of the European Union, inviting expressions of interest.
Ministers have regarded Prestwick Airport as a strategic economic asset, particularly for Ayrshire.
It passed into state hands after being bought by the Scottish government for £1 in late 2013.
The Scottish government said then that the deal would help protect the airport and safeguard thousands of direct and indirect jobs.
Prestwick has been looking to turn around it fortunes, including applying to carry out horizontal space launches from its 2,986-metre concrete case runway.
Transport Secretary Michael Matheson said: “Since the Scottish government bought Glasgow Prestwick Airport in 2013, we have been clear that it is our intention to return the business to the private sector when the time is right.
“The senior management team at the airport has continued to engage with potential buyers and investors to discuss proposals for developing the business under new ownership.
“Good progress continues to be made by the airport to increase revenue, deliver operating efficiencies and pursue exciting opportunities for the future, including Spaceport.”
Mr Matheson added that any expressions of interest would be “considered carefully” before any decision was taken to divest the government’s shareholding in the airport or any part of the business.
In January, it emerged that the debt owed by Prestwick Airport to the Scottish government had risen from £30m to £38.4m.
That was while revenue rose through a doubling of funds from refuelling aircraft at the publicly-owned facility.
Accounts lodged with Companies House showed the holding company made a loss of £7.6m in the year to March 2018, down from £8.6m the previous year.