The aerospace and defense industry and related exchange traded funds (ETFs) may be a good long-term play if activity with Boeing is any indication. A rebound in the global economic activity and greater demand for fleet additions and replacements are just some of the reasons why the  airplane manufacturer is optimistic about the future of the industry.

In Boeing’s (NYSE: BA) 2010 Current Market Outlook, the company calculates that there will be a $3.6 trillion market for orders of around 30,900o new airplanes over the next two decades, according to Zacks Investment Research.

Boeing expects increased demand for single-aisle airplanes, with growth of 69% of estimate airplane deliveries in 2029 and 47% of the projected total value. Twin-aisle airplanes will bring in 23% of total units and 45% of the projected total value.

Growing demand for the single-aisle airplane is partly attributed to the low-cost carrier business model, expansion of air service in emerging markets and unstable fuel prices. The U.S. and European countries will likely be purchasing new aircrafts to replace aging planes.