MEMBERS of the Orient Airlines Association (OAA) have announced 24.5 per cent growth in system-wide operating profit to US$2.2 billion for 1991-92, with Singapore Airlines and Cathay Pacific taking the top profit slots. In contrast, the global airlines group, the International Air Transport Association (IATA), reported a US$790 million operating loss for the same period. However, an OAA board survey has found that Kai Tak holds the record among Asia-Pacific airports for the number of delayed take-offs. ''One out of every three flights is delayed,'' said Mr Saw Leong Beng, director of research and statistics. The OAA's profit growth came in spite of a small decline in the load factor. ''This is a marked improvement over the 32 per cent decline in the previous year,'' said Mr Saw. ''Nine members' operating profit exceeded US$100 million, with Singapore Airlines and Cathay Pacific being the most profitable airlines, registering US$481.5 million and US$453.5 million respectively. ''In contrast to IATA's operating loss for system-wide operations, OAA's achievement can be considered remarkable,'' he said. The number of OAA's international passengers in 1991-92 increased by four per cent to 56.5 million. The number of passengers carried in the region by OAA members grew 3.8 per cent to 39.3 million. Cathay Pacific had the largest regional carriage, with six million passengers - 84 per cent of its international passengers. Operating costs grew by seven per cent to US$18.9 billion, whereas operating revenue increased by five per cent to US$20.5 billion. Mr Saw said that over-capacity had put pressure on yields, while costs remained a constant problem. But, he said: ''An IATA/OAA joint forecast has projected annual growth rates of seven to 8.6 per cent for the next 20 years, while passenger traffic is expected to increase more than four-fold to 375 million by 2010, or a share in excess of 50 per cent of the world scheduled international traffic.'' The airport survey revealed that the constraint of Kai Tak's single runway, limited parking spaces and slots were reasons for the airport only getting 67 per cent of flights away on time. Kimpo-Seoul Airport came first, with a 92 per cent on-time performance.