"The forecast reflects the economic struggles we see today in some of the mature markets," Randy Tinseth, Boeing's vice-president of marketing, said.
Fuel bills for four-engine planes such as the 747 and double-decker A380 have been pushing airlines toward longer-range twin-engine models that burn less kerosene.
Orders last year for Boeing's 777 reached a record 202, while the new 747-8 had only seven sales, according to Boeing's website.
There also will be fewer sales of narrow-body planes, according to the forecast, which accounts for new models from planemakers in China, Canada and Russia. That category, which includes Boeing's 737, makes up the bulk of the global fleet.
He said Boeing's 737 MAX model, revamped with new engines, will be good enough to keep market-share parity with Airbus's A320neo.
Airbus chief operating officer John Leahy said that his goal was to win 60 per cent of the global market for single-aisle planes within the next few years.
Demand is strongest in Asia, where Boeing predicted buyers will get 12,030 new planes by 2031, a 5.1 per cent jump from the 2011 forecast.
Boeing sees fewer purchases in North America, Latin America and the Middle East than a year earlier.
Passenger traffic will rise about 5 per cent a year in the next two decades, Boeing predicted. The US planemaker and France-based Airbus are pushing output to record levels to trim backlogs of more than 8000 jetliners, representing more than seven years of work.
Boeing shares are unchanged in the past year, compared with a 24 per cent gain for those of Airbus parent European Aeronautic, Defence & Space Co. Boeing rose 1.5 per cent to US$74.27 at the close yesterday in New York, while EADS fell 0.2 per cent to €28.43 in Paris.
While Boeing's forecast predicts only a 1.5 per cent gain in aircraft numbers versus last year's outlook, the value of those planes will rise by almost 13 per cent as airlines opt for larger jets, Tinseth said.
The average plane will get about 5 per cent bigger during the next 20 years, Tinseth said.
That will shift the "middle of the market" to jets equivalent to a 185-seat Airbus A321 or 737-900ER, compared with a 150-seater now, such as an A320 or 737-800.
Boeing cited a "sluggish" cargo market in paring its forecast for jet freighters. Until last week's order by FedEx Boeing hadn't sold any cargo aircraft this year, and the market remains "volatile", Tinseth said.
Cargo traffic will gain 5.2 per cent annually, down from a previous forecast of 5.6 per cent, the planemaker predicted.
- Bloomberg