Infratil will not say how long it will persist with trying to find a buyer for its loss-making British airports.
The infrastructure investor wrote $52.6 million off the airports' value, on top of the $10 million operating loss the two airports contributed to its results for the 12 months to the end of March.
Chief executive Marko Bogoievski told the annual meeting of shareholders that Infratil had thought Glasgow airport would benefit from the explosive growth of low cost airlines.
But the reality turned out to be that its main customer, Ryanair, could simply play Glasgow off against competing airports.
Infratil had now exhausted all avenues to try to make that and the Kent airport pay, and the company had been trying to sell them for about a year, Mr Bogoievski said.
"At this moment in time, an asset like that that is actually quite a long-term hold is difficult to sell," he said.
"After a year of trying I don't think you can say you're confident of divesting them but it's our job to exhaust that process."
It wasn't "sensible" to put a timeline on how long the company would keep trying to sell before it considered closing them.