BANGKOK, March 13 -- The Thai navy's patrol aircraft began on Thursday to search the Andaman Sea and the Gulf of Thailand for the Malaysia Airline plane gone missing since last Saturday, but found no trace of it as yet.

The low-flying, turboprop-engined Dornier planes have joined the Thai navy's search mission which started on Monday but still found nothing related to the missing Boeing 777 plane flight MH 370 with 239 passengers and crew aboard.

One of the Dornier planes has joined the search mission by HTMS Pattani fast patrol boat and its helicopter in an extended maritime area around Malaysia's Langkawi and Perlis islands and north of Indonesia's Sumatra island while the other has searched the lower part of the Gulf of Thailand for any flotsam which might possibly be related to the airliner.

A few other patrol boats of the Thai navy have remained on stand-by at Pang-nga and Songkla naval stations but not as yet joined the search effort.

Thai navy chief Adm. Narong Pipatanasai commented that the Malaysian authorities who had asked the Thai navy to help search the seas for the missing airliner, which took off from Kuala Lumpur and was bound for Beijing, had not given much information concerning the exact location or direction of the plane had taken before it lost contact with air traffic control.

However, the Thai navy is not going to call off the search mission anytime soon though no clue has been found so far, the admiral said.

"We will continue to search the Andaman Sea and the Gulf of Thailand for the missing airliner probably until the Malaysian authorities give up the search effort," he said.

The navies of Malaysia, China, Vietnam, the United States and several other countries have begun their respective search and rescue missions since the past six days.

The altitude, direction and speed of the Boeing 777 plane which had lost contact with ground control nearly two hours after take- off apparently remain a mystery to the search and rescue teams.