Boeing announced an improved forecast for the airliner market on Wednesday, forecasting demand for 25,700 planes worth USD$2.1 trillion over the next 20 years.

That was up by 700 planes or USD$100 billion from its forecast a year earlier, a news release from the company showed.

The world's second-largest maker of airliners sees stronger demand for single-aisle, mid-sized twin-aisle and planes as large or larger than the 747 jumbo.

Its long-term forecast for regional jets was weaker than a year earlier.

Its figures assume annual average growth of 4.8 percent in global passenger traffic.

The Asia-Pacific is expected to be the largest market, accounting for 36 percent of the value of total demand.

"Single-aisle airplanes will dominate the market in the next 20 years," said Randy Baseler, vice president of marketing at Boeing Commercial Airplanes.

He said airlines would add mid-sized, twin-aisle planes for longer routes across the Atlantic and Pacific oceans while the very large plane market would account for only about 3 percent of deliveries.

Rival Airbus in December released a 20 year forecast for 17,300 planes worth USD$1.9 trillion, with a far greater focus on large planes where it sees demand for some 1,650 aircraft.

Their forecasts reflect different priorities as Airbus nears completion of the EUR12 billion (USD$14.8 billion) development of its 555 seat A380, while Boeing concentrates on orders for its mid-sized 787 due in 2008.