While the Infrastructure Ministry was notified of the decision on Tuesday, the news was announced on Friday by SHS Aviation, the Chinese-controlled company that bought Aerodrom Maribor at the end of 2016 and signed a 15-year concession contract with the state in early 2017.

The contract will cease to be valid after a six-month notice period, with SHS Aviation saying it would continue fulfilling all of its obligations until then.

The lessee of the Edvard Rusjan Maribor airport has been repeating in recent months that the existing contract was unsustainable economically and that their key motive for the investment had been to develop the airport so as to enable intercontinental flights.

When the existing contract was signed, interest existed on both sides for such a development and the lease conditions were agreed with the idea of starting the upgrade of the airport as soon as possible, SHS Aviation wrote.

The company, which said in 2017 it would secure investments worth EUR 660m, argued that the circumstances had changed significantly, with zoning and concession procedures dragging on excessively and remaining without a clear timeline.

SHS Aviation, whose efforts for a 800-metre extension of the airport's runway have come under attack from environmental groups, said it had put forward different proposals to change the conditions but none had been accepted.

The Infrastructure Ministry said in January that changes to the existing contract were only possible in case of a new call for applications, entailing a cancellation of the contract, which is what the lessee has now decided to do.

SHS Aviation stressed it was not withdrawing entirely from the investment and hopes to reach a mutually acceptable solution in the coming months that would secure a sustainable management model, which will only be possible with appropriate support from the relevant ministries.

The Infrastructure Ministry responded to the announcement with surprise, saying the ministry's current leadership had been actively involved in the search for long-term solutions.

While noting that the 2017 contract had been signed under very clear conditions of cooperation, the ministry said that "less then two years later they demanded state aid".

"For a while they were not even settling their financial liabilities and the frequent talk in the public about their financial difficulties was far removed from the announcements and commitments made when the contract was signed."

"We cannot accept responsibility for potential unrealistic promises made in the past, while we rejected the request for state aid because Aerodrom Maribor failed to meet the legal conditions for it," the ministry wrote.

It said it had expressed readiness multiple times to look for appropriate solutions, "but solutions need to found that will be suitable for as many stakeholders as possible, not only for one side".

The ministry said that "the procedure for selecting the best option for the development of the airport...is under way, as are activities related to the spatial plan for this area".