No pilots or crewmembers of South Korean air carriers failed a government-conducted sobriety test for the past four years, the transportation ministry said Monday.

According to the Ministry of Land, Infrastructure and Transport, all 17 pilots and 61 crewmembers of six local carriers passed a recent sobriety test held in Bangkok, Thailand.

The ministry had dispatched officials to the Southeast Asian country for the previously unannounced blood alcohol level test of South Korean pilots and flight attendants waiting for return flights.

The government regularly conducts sobriety tests on pilots and flight attendants of local airlines after pilots attempting to fly drunk were exposed in three separate incidents in 2010 and 2011.

A pilot or flight attendant with a blood-alcohol level of over 0.03 percent is prohibited from operating or serving on a plane with violators subject to penalties ranging from up to three years in jail or a maximum fine of 30 million won ($25,000), according to the ministry.

Annually, about 15 percent of 5,700 pilots and 12,000 flight attendants of local carriers undergo sobriety tests, mostly conducted just before boarding a plane.

Overseas tests are conducted once or twice a year to make sure they are observing related regulations in other countries, ministry officials said.

No one has failed the sobriety test since the government began holding overseas tests in 2012, they added. (Yonhap)