"For Bangkok to be a strong aviation hub in the region, the long-term vision should still be to have a single airport operation," said Albert Tjoeng, a Singapore-based spokesman for the International Air Transport Association, the global airline industry group.

"Two airports will split passengers, airlines, the AOT's resources and will lead to lower cost-efficiency and inconvenience for passengers," Tjoeng said.

Airports of Thailand (AOT) operates the troubled Suvarnabhumi Airport, which opened in September to replace Don Muang.

On Tuesday, the government said the move back to Don Muang would allow more than 100 cracks on runways and taxiways to be repaired at Suvarnabhumi, as well as ease traffic congestion at the new airport.

The three-billion-dollar Suvarnabhumi Airport, named "Golden Land" in Thai, was supposed to be a gleaming symbol of modern Thailand.

But it has been mired in problems since opening, including the cracks, corruption claims, inadequate toilets and complaints about hygiene standards.

Thai AirAsia, the country's largest budget carrier, said the government should do more to clarify the problems at Suvarnabhumi.

"Authorities have to speed up restoring confidence in the international aviation community," the airline's chief executive Tassapon Bijleveld said.

An aviation industry source in Singapore said the government's decision to re-open Don Muang might also have been motivated by politics rather than safety concerns.

"The current military regime is doing everything it can to discredit the Thaksin era," the source said, referring to former premier Thaksin Shinawatra, who was ousted in a bloodless coup in September.

Suvarnabhumi was one of Thaksin's pet projects. The deposed premier made the airport scheme a personal crusade, once camping at the building site in a show of support.

"One way of discrediting the Thaksin regime is by showing his big, pet project, Suvarnabhumi Airport, was wrecked not only by corruption but also incompetence," the source said.

Meanwhile, the Airlines Operator Committee, which groups 68 foreign airlines in Bangkok, said it opposed the re-opening of Don Muang, adding one international airport should be enough for Thailand.

"Our standpoint is that operating a single airport at Suvarnabhumi is the best thing. If Suvarnabhumi is already congested, we should utilize the existing facilities," said Sopin Daengteth, the committee's chairperson.

Suvarnabhumi has capacity of 45 million passengers per year and Thailand hopes the new airport will further boost the country's tourism industry, which accounts for six per cent of the economy.

But Anek Srishevachart, president of the Association of Thai Travel Agents, said he was worried that confusion arising from having two international airports could dent growth in the tourism industry.

"It is not the right decision made by the government," Anek said, adding that the government should have consulted airline and tourism executives first.

"Having the dual international airports would create great inconvenience and confusion for airlines, travel agents and tourists. The impact on tourism from such a policy will be very huge," he said.

Richard Pinkham, a Singapore-based aviation analyst at the Center for Asia Pacific Aviation, agreed it could create problems for passengers but argued the two airports could be better for Thailand's air traffic in the end.

"In the short-term, it does cause confusion for sure, but in the longer-term, the initial confusion will be a small price to pay for more capacity," Pinkham said.

"With current rates of growth, it won't be too long before brand-new Suvarnabhumi is overburdened," he said.

Agence France-Presse