IN a year in which KLM, the Dutch national airline, marks its 75th birthday there is reason to also celebrate the success of the World Business Class service it introduced at the end of last year. ''The response to the service has been amazing,'' said Ton van der Werf, KLM general manager for China, Hong Kong and Macau. ''Almost every flight is now full.'' The secret to this success has been the decision to dispense with first class, expand the business class section and upgrade service. This translates into increased leg room - the largest in the business, according to Mr Van der Werf - greater recline in the seat, integral individual entertainment systems, and a wider choice of meals. He said: ''To serve our customers in this market, between 60 and 70 per cent of whom are ethnic Chinese, we have an interpreter on each flight to liaise between passengers and cabin crew. ''The movies on the personal entertainment system have sub-titles, and we even publish a Chinese in-flight magazine.'' The personal entertainment system is state-of-the-art. Seven channels are available for passengers to choose from, including one showing classic and contemporary movies, another offering news and one airing sports features. The number of seats in business class has increased from 38 to 52, with 30 on the upper deck of Boeing 747-400s that fly from Hong Kong to Schiphol Airport four times a week. ''Schiphol is the premier airport in Europe and one of the best in the world,'' said Mr Van der Werf, adding that it was the blueprint for Changi Airport in Singapore. The latest plans call for the train station to be moved to a new site to make way for Schiphol Plaza - a 55,000-square-foot shopping and passenger area that will contain 27 retail outlets and five food outlets. The plaza is due to open next year. ''The other attraction of Schiphol, of course, is its location. It is seen not only as the gateway to the Netherlands, but as a gateway to Europe. And that is how travel agents here promote it,'' Mr Van der Werf said. ''People in the Rheinland-Westphalia region of Germany look on Schiphol as their international airport, as do people in Belgium. This is even true of British nationals, as we offer excellent connections to UK airports through our partner airline, Air UK. But it is KLM's links with another partner - Northwest Airlines of the US - which have received wider coverage and are better known in Hong Kong. ''The co-operation with Northwest, which dates back to 1989 when KLM took a 20 per cent stake in the US carrier, has gone further than any other and resulted in the first truly global airline alliance,'' said Mr Van der Werf. ''The World Business Class service is being offered by both airlines: we are doing joint promotions, marketing and scheduling. This was almost extended to a joint office in Hong Kong, but practical considerations mean that will have to wait for a while - Something which passengers will not have to wait for is the use of lounge facilities at Kai Tak airport, as KLM and Northwest now share a lounge there. As the oldest international scheduled airline in the world, KLM has built up an extensive network. This has been expanded by the link up with Northwest, resulting in a route system that spans the world. Together they cover more than 380 cities in 81 countries, allowing passengers to fly on the one ticket and having to check in luggage only once. Cargo also plays an important part of KLM's business on the Hong Kong-Amsterdam route, with fresh flowers one of the major imports into the territory. Other imports flown in by KLM include artists and paintings from a country which has a rich tradition in art. ''We actively sponsor many events which promote the Netherlands,'' said Mr Van der Werf. ''Last year, we were involved in the Holland Village event at Kowloon Park, flying over a well-known Dutch painter. The whole event was a great success and will be repeated this year.''