Of THE WALL STREET JOURNAL

Boeing Co. BA, -1.06% projects a $4.5 trillion jetliner market over the next 20 years for 34,000 new commercial jets, up nearly a half trillion dollars from the previous year's estimate on higher jetliner prices and continued inflation.

"The world's aviation market is broader, deeper and more diverse than we've ever seen it," said Randy Tinseth, Boeing Commercial Airplanes vice president of marketing in a presentation in London on Tuesday. Though he cautions there are troublesome signs ahead for the world's airlines with struggling economies in Europe and slowdowns in global air cargo.

As it looks out to the rest of the year, Boeing anticipates 2.5% growth in the global economy, but the company's long-term trend points to 3.2% yearly growth over the next 20 years as part of its annually updated current market outlook.

That growth will drive a 4% increase in the number of people flying each year and 5% annual improvement in airline traffic, leading to a doubling of air travel over the next 20 years despite near-term uncertainty.

Boeing now estimates that 41% of the new deliveries will go to replacing older less fuel-efficient jets currently in operation today.

Asia Pacific, including China and India, will require the largest share of the new aircraft with 12,030 deliveries up from 11,450 the year prior, followed by Europe and North America in a distant second and third at 7,760 and 7,290 aircraft, respectively.

Latin America and the Middle East markets require 2,510 and 2,370 jets between 2012 and 2031. The Middle East, which has led deliveries from Boeing and Airbus in recent years, is now forecast to need 6% fewer aircraft than Boeing's last estimate.

Additionally, the Commonwealth of Independent States in the former Soviet Union, are expected to account for 1,140 deliveries and despite being the smallest market by units, Africa will require 900 aircraft, up 12.5% year over year and the single biggest percentage gain of any market.

Overall, Boeing expects the world will need 500 more jets than it forecast in the 20-year period to follow 2011, ranging from small regional jets and single-aisle workhorses to large long-range twin-engine jetliners and the largest jumbo jets.

The greatest share will come from deliveries of single-aisle aircraft, like the Boeing 737 and Airbus A320--and updated and more expensive models the 737 Max and A320neo due later in the decade--will see 23,240 handed over to the world's airlines in a slightly lower number than forecast last year, but still worth $2.08 trillion.

Despite being down slightly from last year's 23,370 estimate, Boeing and Airbus are in the process of accelerating output of their smallest products and by the end of 2014, the two largest jet-makers will deliver 84 single-aisle jets per month, or 42 each.

Airbus announced Monday it would open a U.S. assembly site in Mobile, Ala. for its A320 jets, with first deliveries beginning in 2016.

The nearly 13% increase in the overall value of the market over the next two decades is due in large part to an updated estimate of the number of twin-aisle aircraft, like Boeing's 777, 767 and 787 Dreamliner. The company now expects to see 7,950 deliveries in the category, up 620 aircraft from its estimate a year prior, driving the market value higher by $310 billion to $2.08 trillion.

Boeing is sharply increasing deliveries of its twin-aisle aircraft, with plans to accelerate to 8.3 777s per month, or 100 annually, starting in early 2013 and 120 Dreamliners per year by the end of 2013.

The largest passenger aircraft in the world remains the smallest overall market by units with Boeing now expecting 790 deliveries, worth $280 billion, down slightly from last year's 820 aircraft. Boeing and arch-rival Airbus have continually diverged on this estimate as Airbus continues to advance its five-year-old double-deck A380 in the market.

Regional jets, a category left to Brazilian Embraer SA (EMBR3.BR), Canadian Bombardier Inc. BDRBF, -2.48% and newcomers Russian Sukhoi Civil Aircraft Co. and the Commercial Aircraft Corp. of China, will see deliveries topping 2,020 worth $80 billion over 20 years, up slightly from the year prior.

Boeing also estimates that the slower overall economic growth will hold down cargo traffic growth to 5.2% annually, down from 5.6% the year prior, but will still result in a near doubling of the cargo fleet to 3,200 aircraft, up from 1,740 aircraft today, made up of both new and converted passenger jets.

Write to Jon Ostrower at jon.ostrower@wsj.com