Details have emerged about the U.S. Air Force's desire to buy several hundred short-takeoff and vertical landing (STOVL) F-35B Joint Strike Fighters, and this has angered  some program managers and Pentagon officials. The F-35B is designed to take-off and land vertically, mainly for operation from smaller carriers and improvised fields. The primary customers are the U.S. Marine Corps (with plenty of deck space on amphib ships) and the Royal Navy. Initially, it looked like the Air Force was going to simply buy a bunch of F-35Bs with a different paint job, but have recently expressed a need for a modified version of the jet. 

The F-35 was designed to take one basic single-engine aircraft body, and through the use of computer-aided design tools and different parts, become essentially three different aircraft. The F-35A, the stock model for the Air Force, the F-35B the short-takeoff version, and the F-35C would be the Navy's version, with reinforced parts to take up the stresses of catapult launches and arrested landings on aircraft carriers. By using common electronics, parts, and one production line, the goal was to keep the cost of the production run down for everyone. 

Air Force officials would like an F-35B version with an internal 25mm cannon instead of the Marine Corps's gun in an external pod, plus a refueling probe instead of a boom receptacle, a larger wing (possible the Navy's wing design) for more fuel and lift, and a modified propulsion scheme to emphasis short takeoff and landing, while dumping vertical landing out of the capability set. 

Critics are not happy about the "modified" version and think the Air Force should suck it up and take the F-35B performance hit rather than running up the bills to design and build an F-35D. Advocates are intrigued about the idea to take the core F-35 design and get another plane type out of the family. The Air Force wants to have a longer-range aircraft, and ditching vertical takeoff equipment and adding a bigger wing is the quickest path to get what they want. Overseas customers have also expressed an interest in this version. The targeted combat range of the existing conventional F-35 variant is around 1000 kilometers, with the STOVL version having slightly shorter range. Doug Mohney