SEOUL (REUTERS) - South Korea is considering tightening regulations for pilots seeking certification to convert to flying new aircraft after the fatal crash of an Asiana Boeing 777 plane in San Francisco, a government source said on Tuesday.

Asiana Airlines' chief executive also said the carrier plans to beef up simulated "non-precision airport approach" training as the role of its pilots on the crash comes under increasing scrutiny.

The Asiana Airlines Boeing 777 was flying 25 per cent slower than normal for a descent in the run-up to Saturday's crash, according to US National Transportation Safety Board chairman Deborah Hersman.

Mr Lee Kang-kuk, the pilot at the controls of Asiana's 214 flight to San Francisco, was training on Boeing 777s, and was making his first attempt to land the jet at San Francisco airport. His supervisor was making his first flight as a trainer.

"This accident made us rethink our regulations policy," the government official dealing with aviation regulations told Reuters. "We are already reviewing various measures and gathering information to tighten regulations (on issuing type certification to pilots converting to a new aircraft)."

The crash killed two teenage Chinese passengers and injured more than 180 other people.

Seoul has tightened aviation regulations since a plane belonging to flagship carrier Korean Air crashed in Guam in 1997, killing 228 people and later prompting a downgrade of South Korea's aviation rating by the US Federal Aviation Administration to Category 2. The rating was restored to Category 1 in December 2001, enabling Korean carriers to open new routes, which they were not allowed to do under the lower category.

The government source said South Korea will also widen inspection to include more long-haul flights and routes to overseas airports such as San Francisco.

"From this year, we've started a new programme that includes our inspector join(ing) the cockpit to monitor pilots' operation to long-haul destinations and 13 airports with tricky landing environment such as San Francisco," the source said.

San Francisco airport is surrounded by water, which can make distances harder to judge.

Asiana chief executive Yoon Young-doo has refused to blame pilot error for the crash and said on Tuesday: "The two pilots on the plane have enough qualifications, having flown to San Francisco 33 times and 29 times, respectively." However, he added that Asiana planned to strengthen simulated training, especially for non-precision airport approach, referring to a visual landing, as was used by the flight on Saturday.

Mr Lee, the pilot under training, was experienced, with almost 10,000 hours flying time.

Currently Asiana pilots have to fly 10 flights and a total of 60 hours on a 777 to complete its training programme, a spokesman for the airline said. Mr Lee had completed eight flights and 43 hours. His round-trip to San Francisco would have given him the remaining two flights and 17 hours to make him fully qualified to fly the double-engine jet.

Landing is part of the training programme, and it is common practice for pilots in training to land under supervision as part of the type certification process.

Mr Jung Yun-sick, a former Asiana pilot and now a professor at Jungwon University, told Reuters that any new measures were unlikely to increase the number of training hours for pilots trying to shift to a new aircraft.

"The requirement used to be 60 flights of a total of 100 hours some 15 years ago when I was with Asiana," he said, the same as it is now. "It was quite intensive at the time as they didn't have much data on what is really appropriate level of training. But now they have enough data for this and the current level is what is generally accepted globally."