Kazakhstan’s Air Astana has had to cancel the planned launch of direct flights between Astana and Ulaanbaatar in Mongolia from June 2 due to what it called the ungrounded revocation of permission by the Civil Aviation Authority of Mongolia (CAAM).

Kazakhstan and Mongolia signed an air services agreement in 1992 and a memorandum of understanding establishing the number of flights allowed in 2014. According to Air Astana, the CAAM granted authorization to start flights this March, but in April it withdrew its permission. The airline said it started the flight permission application process—a procedure that normally takes two months to complete—eight months before the planned first flight. It passed an audit by Mongolian authorities, who later reported “zero findings.”

Despite diplomatic efforts by the Ministry of Foreign Affairs and the Ministry of Industry and Development of Kazakhstan, the CAA refuses to reverse its revocation due to what Air Astana characterized as an ungrounded and changing list of reasons, including the aforementioned audit, the lack of availability of Ulaanbaatar Airport in June for the July ASEM Summit and an alleged blacklisting by ICAO. Air Astana does not appear on any blacklist, however.

“Kazakhstan believes that Mongolia is in breach of the provisions of the Chicago Convention, and will refer the matter to the ICAO Council accordingly,” said Air Astana in a statement.