Thailand, which has been trying to improve air safety standards for months, kept a brave face yesterday as the United States aviation authority downgraded the kingdom's ratings.

Although the move has no immediate impact on Thai airlines, there are fears that it could trigger more serious knock-on effects on one of Asia's fastest-growing air hubs.

The US Federal Aviation Administration (FAA) revealed on Tuesday that it had downgraded Thailand's Department of Civil Aviation from Category 1 to Category 2 because it did not meet "minimum international standards".

It effectively blocks Thai airlines from starting new flights to the region even though no Thai carrier currently flies to North America.

Thai Transport Minister Arkhom Termpitayapaisit told reporters yesterday that one of the weak points identified by the FAA was that there were simply not enough skilled aviation officials.

"Thailand has a growing fleet of airplanes, both in quantity and diversity, and we have difficulty keeping up with the training of auditors and inspectors," he said during the press conference.

The Department of Civil Aviation needs to rethink its personnel management strategy for the industry's long-term sustainability, he added.

Thai Deputy Prime Minister Somkid Jatusripitak told Reuters that the financial impact of the FAA downgrade is small, "but there is an impact in terms of (business) sentiment".

Thailand has been trying to beef up regulatory standards since early this year, when the International Civil Aviation Organisation raised concerns about the quality of oversight in the country's aviation sector. This led to greater scrutiny of Thai airlines, as well as temporary bans on new and charter flights by South Korea, Japan and China.

Of greater concern now is an audit by the European Aviation Safety Agency, the results of which are due to be announced later this month. If that leads to a downgrade, it would affect state-owned carrier Thai Airways, which flies to Europe.