Earth's airspace is set to have twice as many airliners flying as now, and that's just the civilian airplane traffic forecast to grow in the next two decades.

Boeing Co., which released the 20-year outlook for airliner demand, said growth would be worth $4.8 trillion. Buyers in the Asia-Pacific region, which includes several Latin American countries, are seen to figure prominently in those lucrative projections.

Although Boeing's forecast outlined opportunities opening up in emerging markets worldwide specifically in airplanes business, with an accompanying boom expected in security industries, other recent surveys point to a different picture in defense aviation.

In defense and military procurement programs across the planet, unmanned aircraft systems are driving major purchase reviews that are seen likely to result in further cuts in combat personnel, less manned aircraft and more computerized warfare.

All recent defense air shows in Latin America and Europe featured a growing variety of UAS delivered as vehicles in all shapes and sizes.

In the airline business growth, Boeing said single-aisle jets would drive the demand upward -- an indication of growing regional air transport. Company consolidation and mergers are seen behind a current spurt in small jets, with local manufacturers like Brazil's Embraer seeking an edge on price and flexible payment terms.

Both passenger traffic and cargo traffic are expected to grow 5 percent annually, Boeing said as it unveiled its annual Current Market Outlook.

"This forecast gives us confidence as we increase our production rates and invest in new products like the 777X and 787-10X," said Randy Tinseth, Boeing Commercial Airplanes' vice president of marketing.

"Airlines are demanding more efficiency and that is exactly what we'll be giving them."

The single-aisle market, served by Boeing's Next-Generation 737 and the future 737 MAX, is the main driver of the forecast, Boeing said.

In that segment alone, 24,670 new airplanes will be needed due to the growth of low-cost carriers and airlines from emerging markets.

Widebodies, such as Boeing's 747-8, 777 and 787 Dreamliner, also make up a large part of the forecast. In that segment, 8,590 new airplanes will be needed, the demand fueled in part by airlines replacing their older fleets with new, more fuel-efficient airplanes.

The market for new airplanes will continue to become more geographically balanced in the next two decades, Boeing said.

An earlier forecast by Boeing's main European rival Airbus said it calculated the expected rise on factors such as population growth, urbanization, emerging markets, innovation and environmental impact.

Airbus said it foresees through 2031 the need for some 27,300 passenger airliners with seating capacities of 100 seats or more along with nearly 900 new factory-built freighter aircraft.

The company's global market forecast last September also anticipated a more than doubling of the world's overall passenger aircraft inventory from about the current 15,500 to more than 32,500 by 2031.

Although the Boeing report doesn't go into potential challenges to its market share, Boeing and other U.S. and European manufacturers are also up against growing competition from emerging market planemakers like Embraer in smaller passenger jets and cargo aircraft.