The potential that global air travel might grow by 4.7% annually over the next 20 years provides a great opportunity for aerospace manufacturers and prudent, forward-thinking investors. The world might need new aircraft worth up to $4.8 trillion to meet future demand . 
 
Dreamlining
Boeing Commercial Airplanes, a division of Boeing (NYSE: BA), is one company that might prosper if that growth does materialize.
 
The maker of the iconic 747, the popular 737, and the recently introduced 787 Dreamliner presently derives about 60% of its revenue and 80% of its gross profit from commercial aviation. As other portions of its business, such as defense, decline, Boeing will have to rely on the commercial side for much of its future growth.
 
Boeing can probably benefit from two aircraft already in production: the upstart, high-tech, two-year-old 787 and the old standby, the 737, which was first built in 1968.
 
Boeing projects that up to 1,750 total aircraft could be built over the life of the Dreamliner program . The 787 has list prices ranging from $211 million to $289 million, depending on the model type, but typically sell at a discount. Even so, Boeing might realize revenues and profits in the "tens of billions of dollars" range over the next decade or so.
 
The 737 is the best-selling airliner in history. Over 7,600 have been built since 1968, and there are orders in place for 3,000 more. Some of those orders are for an updated version of the aircraft, the "Max." This revamp will be ready to fly in 2017, and it should go into revenue service shortly after that. The 3,000 orders for 737s alone could also bring in tens of billions in revenue and profit, based on average selling prices of $80 million to $90 million each  .
 
United Supplier
Other companies like United Technologies (NYSE: UTX), a fellow member of the Dow Jones Industrial Average index, would also benefit from growth in commercial air travel. Its aerospace and propulsion segment, which includes UTC Aerospace Systems (UTAS) and Pratt & Whitney (P&W), provides more than 40% of the total revenue and earnings for the corporation, and will become even more important for the company going forward. Like Boeing, UTC will have to rely more and more on its civilian-focused business because of pending government defense cutbacks.
 
Last year, UTC acquired former rival Goodrich and merged it into existing operations. The new entity, UTAS, is now a "one-stop shopping" source for aircraft subsystems that air-framers like Boeing can tap into. It can also use its newly expanded size to produce those parts more efficiently and profitably.
 
P&W has been a jet engine innovator from the earliest days of supersonic travel. It's now offering a new line-up of "geared turbofan" (GTF) jet engines, using innovative technology that results in lower audible noise and reduced fuel consumption and carbon emissions -- key goals of both airlines and governments.
 
P&W will supply the GTF for new aircraft such as the Airbus A320neo and Bombardier C-series, which are being developed to help meet future industry growth. More than 3,500 orders exist for the new engine so far . By 2020, this could bring in up to $12 billion in additional revenue for UTC's engine business, doubling 2010 levels --- a sturdy 7% compounded annual growth rate. 
  
Conclusion
With air travel expected to grow about 2.5 times in the next two decades, aircraft manufacturers have the opportunity to grow along with it. Boeing and United Technologies both depend on aerospace for a sizable chunk of their success, and both are now gearing up with products that would allow them to benefit from an increase in the number of miles flown by the public.
 
Investors with an eye out for the long-term should consider hitching a ride with these companies in the friendly skies. Watch for any additional aircraft order announcements or airport expansion plans in the works to provide a hint that an upward trend is indeed under way.