One success story for the defence industry is Lockheed Martin's workhorse fighter bomber, the F-16, which first entered service in 1978.
The 4,500th F-16, for the Royal Moroccan Air Force, rolled off the production line in April and Lockheed believes it has potential for at least 100 new orders in the pipeline. But the big money-spinner now is the impending demand to upgrade the versatile aircraft with new radars, navigation systems and electronic warfare management systems.
Bill McHenry, Lockheed's F-16 business development director, said the company expects to sell about 550 upgrade kits for the jets.
The United States Air Force plans to spend about US$2 billion (Dh7.34bn) to upgrade 300 of its F-16s and has selected Lockheed Martin as the prime contractor.
Lockheed has also secured a $1.85bn contract to upgrade 145 of the aircraft for Taiwan and a $94.7 million contract to retro-fit an additional 12 for the Oman before May 2016.
But Lockheed will face competition with companies such as Boeing and BAE Systems North America, who are developing their own upgrading packages.
Boeing is already active on a programme aimed at "dronizing" F-16s - developing an unmanned version to use as an aerial target for training purposes.
Meanwhile, South Korea selected BAE Systems to retrofit its 134 F-16s in a contract valued at between $750m and $1.1bn.
