The Ministry of Land, Infrastructure and Transport has sent a letter of protest to the U.S. National Transportation Safety Board, displaying unease over the ongoing investigation into Asiana Airlines Flight 214.

The ministry on Saturday faxed a two-page letter to NTSB chairperson Deborah Hersman, demanding that the U.S. board implement an impartial investigation, according to officials on Sunday.

The NTSB should provide information related to the plane crash on a regular basis and from an objective perspective, the ministry said in the letter.

It also demanded that the NTSB abide by international protocol, implying that the board has so far revealed too much information to the public.

Ever since the plane crash-landed on July 6 in San Francisco, killing three passengers and injuring many others, the Korean ministry and the U.S. board have largely been at odds over the cause of the accident.

According to the International Civil Aviation Organization rules, the investigation is to be led by the United States, and Korea is to play a supporting role as the plane’s country of registration.

The NTSB, though it refrained from jumping into conclusions, repeatedly underlined that no flaws had been detected in the plane or the airport’s control system. Such stance added weight to the speculation that the accident may be attributable to pilot negligence.

“No evidence of mechanical failure was found, whereas the flight data records showed that the pilots failed to detect the abnormal flight altitude and speed,” Hersman said once again on Thursday.

The ministry, on the other hand, said that such unfiltered information may lead to prejudice and it needs to be administered more carefully.

“The government announcements should be based on facts and the pilots’ testimonies first need to be verified (before they may be opened to the public),” said Choi Jeong-ho, the ministry’s aviation policy director last week.

“We need to reconsider whether the information release is indeed necessary to clarify the reason for the accident.”

The Air Line Pilots Association, the world’s largest aviation workers’ labor union, also criticized the U.S. organization for its rash announcements.

The NTSB, however, shrugged off such accusations and claimed its key focus is transparency of the investigation.

Amid such conflicts, Minister of Land, Infrastructure and Transport Suh Seoung-hwan is to hold an emergency safety measure session on Monday with top executives of local airline companies.

Also, Asiana is considering filing a lawsuit against a local broadcaster in the U.S. which used discriminative terms when disclosing the names of the pilots, the airline officials said Sunday.

Local news station KTVU earlier described the names of the four pilots as Sum Ting Wong, Wi Tu Lo, Ho Lee Fuk, Bang Ding Ow.

It later apologized for the mistake, claiming that the sarcastic names had been confirmed by an official of NTSB. The corresponding employee, however, turned out to be an intern with no authority over the release of information.

By Bae Hyun-jung (tellme@heraldcorp.com)