The U.N. body regulating world air traffic says Thailand has failed to meet a deadline for addressing safety concerns about its oversight of its airlines, so it has been added to a list of nations whose aviation authorities fall short of international standards.

A spokesman for the International Civil Aviation Organization, Anthony Philbin, said Friday in an email from the group's headquarters in Montreal that its main concern focused on Thailand's ability to conduct air operator certifications.

ICAO audited Thailand in January, and in March gave Thai authorities 90 days to rectify shortcomings it had found. Thailand failed to meet the deadline and joined 12 other nations found deficient in managing their airlines: Angola, Botswana, Djibouti, Eritrea, Georgia, Haiti, Kazakhstan, Lebanon, Malawi, Nepal, Sierra Leone and Uruguay.