The company that had been chosen to buy Prestwick Airport from the Scottish government withdrew from the deal.
The airport became public property in 2013, after being closed following heavy losses.
Transport Secretary Michael Matheson told MSPs that the preferred bidder – who has never been named – “does not wish to complete the purchase”.
He indicated in a letter to Holyrood that the reason was linked to the impact of Covid-19 on the aviation industry.
Mr Matheson said Scottish ministers “will reflect on future options for the company”.
The Scottish Tories called the announcement “disappointing … but not surprising”.
Party transport spokesman Graham Simpson said: ‘Scottish airports are in crisis due to the pandemic. Thousands of jobs depend on the success of all of our airports and we need to see SNP action now. ”
Colin Smyth, of Scottish Labor, said the Scottish government should draw up a clear plan for operating the publicly owned airport if the sale of the airport at a fair price cannot be guaranteed.
Ministers viewed Prestwick Airport – where 300 people are directly employed with 1,400 additional jobs supported, as a strategic economic asset – in particular for Ayrshire.
The Scottish government announced in June last year its intention to sell the airport.
Mr. Matheson later revealed that the bids for the state-owned airport were still under consideration, despite the October 4 deadline expiring.
Last December, Prestwick Airport reported a “major improvement” in its financial performance over the previous 12 months.
Accounts filed with Companies House showed the Scottish government-owned airport reduced operating losses by £ 3 million to £ 1million.
At the start of last year Prestwick Airport’s debt to the Scottish government had risen to £ 38.4million.
The debt reflected the last years of losses that have accumulated after Ayrshire Airport was saved from closure by the government takeover.
The history of the Prestwick Airport sale
The Scottish Government bought Prestwick Airport for £ 1 in November 2013 after its former owner, Infratil, booked it for closure following heavy losses.
Ministers said at the time that the deal would help protect the airport and save thousands of direct and indirect jobs.
The government has since invested tens of millions of pounds in an effort to turn around its fortunes, including asking for horizontal space launches from its 2,986-meter concrete runway.
Ryanair remains the only regular passenger carrier in Prestwick, but the airport is also used for transatlantic freight and fuel stopovers.