DEMAND for flights out of Singapore has soared, leaving more and more passengers grounded on the wait-lists of airlines because supply cannot keep up.

The message from travel agents: If you want to fly, get in the queue and book early.

Fuelled by a buoyant economy and attractive air fares as airlines compete in an increasingly aggressive market, global passenger traffic reached an all-time high of 4.4 billion last year, a 4.8 per cent increase over 2005.

According to data from the International Air Transport Association (Iata), which represents more than 240 carriers, international passenger traffic grew 6.5 per cent between January and May, compared with a year earlier, but capacity grew slower at 5.6 per cent.

These trends have hit hard in Singapore.

Miss Alicia Seah, vice-president (leisure) of UOB Travel Planners, said: "The market started picking up in 2004 and 2005, but we have really seen it peak recently with very strong demand for business- class travel especially."

Hot destinations out of Singapore include Australia, Europe, the United States, Japan and China.

"These days, business-class seats are usually the first to be sold out," she said.

While many Singapore residents travel in June, November and December, Changi Airport's hub status - with 79 airlines operating a total of 4,180 scheduled flights a week to 185 cities - means it can be tough to get seats out of Singapore during other months too.

One reason why supply has not been able to keep up is the delayed delivery of the Airbus 380 superjumbo, which can carry 555 passengers in three classes - over 100 more than the Boeing 747, which is the largest plane now flying.

The move to offer more spacious premium seating by top-line carriers such as Singapore Airlines is also eating into the total number of seats available by about 10 per cent to 20 per cent.

The phasing out of the B-747s, which some carriers are replacing with the smaller Boeing 777 that typically carries about 300 passengers, has not helped matters either.

That demand is growing faster than supply is clear from looking at SIA's monthly operational data.

Capacity actually fell by 1.5 per cent in April compared with the same month last year. It was the first time such a fall had been registered since June 2004.

But in the same month, the number of passengers carried jumped by 5.3 per cent.

May and June saw a similar drop in capacity.

The result: Load factors - the number of seats filled per aircraft - went up.

In the first six months of the year, SIA's load factor averaged about 80 per cent, compared with about 76.4 per cent in the first half of last year. This meant there were plenty of full flights. British Airways, which flies to Sydney and London from Singapore, also filled more than 80 per cent of seats across its network last month, a spokesman said.

Qantas was also experiencing strong demand for its Sydney and London services out of Changi, a spokesman said. According to Iata, passenger load factors increased to a record 76 per cent across the industry last year.

SIA believes the situation will improve soon: "We would expect growth in capacity to resume within a few months as the A-380s begin being delivered (from October), said SIA spokesman Stephen Forshaw.

"But the growth in carriage will likely continue to rise in buoyant, high-demand areas. And within the next few years, as more and more A-380s come on line, you will see capacity growth rise to quite high levels."

Administrative officer Esther Ching, 40, who is planning a trip to Tokyo in November, is not taking any chances.

"The moment year-end air fares are released next month, I intend to make my booking," she said.

karam@sph.com.sg