Following several concerns regarding Thailand's aviation safety, US-based, Federal Aviation Administration, has downgraded the safety rating of the country's aviation industry.

Thailand's rating is now "Category 2" which means that its civil aviation authority is deficient in one or more critical areas or that the country lacks laws and regulations needed to oversee airlines in line with international standards.

The downgraded safety rating could hamper operations of Thai airlines worldwide.

The airline can continue its service to the United States but will not be allowed to establish new services.

Thailand's Prime Minister, Prayut Chanocha, has ordered air transport officials to improve flight safety because of internation criticism.

The department said yesterday: "Since the release of Thailand's results from the audit report by ICAO last March, CAD has not permitted any new flights from Thai flight companies to operate other than those that already exist.

"CAD will closely monitor ICAO's safety assessments on the Thai authorities and keep track on their improvements made in response to the report results. We will take action at an appropriate time in order to guarantee safety of air traffic."

Thai Airways president Charamporn Jotikasthira said its business would not be affected.

"Thai confirms its commitment to aviation safety standards, and assures all that Thai operates with the highest international aviation safety standards," he said.

While none now operate direct routes to the US, the FAA's downgrades are often matched by other global aviation authorities, raising the prospect of restrictions on routes to Europe or East Asia.

Thailand's military government ordered an overhaul of the civil aviation authority after ICAO made an initial negative assessment in March, but it could not meet a deadline for rectifying all the problems.

An audit report on aviation systems including Thailand's will come from the European Aviation Safety Agency next.