Urgent expansion is reportedly needed at Suvarnabhumi Airport, as well as improvements to the airport’s “tarmac, taxiways and apron area because of soft spots," Iata director-general and chief executive officer Tony Tyler said.

It comes after the US Federal Aviation downgraded Thailand’s safety ratings in December last year. The UN’s International Civil Aviation Authority also downgraded the country in June 2015, giving it a red flag for missing a deadline to work on safety concerns, Reuters reported.

"Aircraft get stuck in the soft surface due to substandard materials," Tyler said in an interview in Bangkok, after returning from the Singapore Airshow.

The airport handles 52 million passengers each year. Tyler said it had a significant regional and global role but needed urgent expansion of its terminal capacity.

"It was designed to handle 45 million passengers annually, but it exceeds that today and traffic is still growing at an annual 10 percent rate," he said.

"Overcrowding is a serious issue that will become critical quickly," Tyler said.

Thai airport operator Airports of Thailand said it was aware of the problems flagged by Iata and had readied several measures to improve runways using concrete and expand capacity, which were awaiting government approval.

"We have prepared short- to medium- and long-term plans to solve the problems," Sirote Duangratana, general manager of Suvarnabhumi Airport, told Reuters.