Airbus is forecasting demand for 28,200 passenger and freighter aircraft worth nearly $4 trillion over the next 20 years, an increase of 1.2% on its previous global market outlook.

The latest forecast, released during an event in London on 4 September, covers the two decades to 2031.

Airbus expects passenger aircraft with at least 100 seats to account for 27,350 deliveries, up from last year's estimate of 26,951. The manufacturer puts the overall value of the passenger fleet at $3.7 trillion.

Of the total deliveries some 10,350 will go towards replacing current aircraft.

Airbus says the positive forecast "reconfirms an upward trend" regarding the rate of new deliveries, adding that passenger traffic will rise at an average 4.7% per year over the period.

The deliveries will include over 1,700 large-capacity aircraft, such as the Airbus A380, of which 1,330 will be passenger jets - a figure virtually unchanged from last year's forecast.

The passenger aircraft will be worth about $500 billion, accounting for just 5% of airframes but 13% of the overall value of passenger deliveries. Asia-Pacific and Middle Eastern customers will head the high-capacity demand, with 46% and 23% respectively, followed by European customers with 19%.

Airbus forecasts demand for 6,970 aircraft in the twin-aisle sector of which passenger types will make up 6,500 - a slight rise on last year's 6,425. Asia-Pacific remains the primary demand region, followed by Europe and North America.

The airframer predicts higher demand in the single-aisle sector with 19,500 passenger deliveries, up from 19,165 in its previous forecast, and says around 30% of these will go to low-cost operators.

Airbus says the changes will more than double the global passenger fleet from the current 15,550 airframes to more than 32,550. The freighter fleet will rise from 1,600 to 3,000 aircraft.

"Emerging economic regions will represent more than half of all traffic growth in the next 20 years," it adds. "Increasing urbanisation and the doubling of the world's middle classes to 5 billion people is also driving growth."

Chief operating officer for customers John Leahy says that domestic Chinese traffic will "overtake" domestic US traffic by 2031, becoming the largest traffic flow category.

"Aviation is not just essential for international commerce but also for domestic economies too," he adds.