"Fly before you buy"
From the Chicago Tribune of 21 March 2013, that F-35 Lightning fighter program in peril, not going well but that commitment already made.
"FOCUS F-35 STRIKE FIGHTER"
"Too costly to fail, warplane lags on"
"How 1 plane for all became a free-for all"
"Conceived in the 1990's, the F-35 program was supposed to use the same airframe to produce planes for the Air Force, Navy and Marine Corps, with only modes t modification. But the services all sought major changes to meet their needs, reducing commonality among the the three variants. Instead of meeting the original plan of being about 70 percent similar, the three versions now are about 70 percent distinct, which has increased costs by tens of billions of dollars and led to yearslong delays"
And from that same article those quotations most germane as to the difficulties as faced by the F-35 program:
"We have three airplane program running in parallel" . . . "They are very very different airplanes."
"I am - - after many years of frustration and setbacks - - encouraged that the overall program is moving in the right direction."
"It's essential for us," . . . "We don't have another option."
One plane for three services with the intention that commonality be 70 % is now 70 % dissimilarity!
The U.S. Marines wanting a vertical-takeoff-landing [VTOL] and the U.S. Navy wanting a plane with: "larger wind to enable short takeoffs from aircraft carriers".
The U.S. Marines in dire need of a replacement for the Harrier "jump-jet" VTOL seen as a necessity.
And for all three services NO OTHER option besides the F-35 even under consideration.
Export too a consideration, a variety of nations have already [?] made that decision to purchase the F-35.
With regard to the VTOL capability, we have this from an acknowledged aviation authority:
"VTOL uses so much energy just to lift the plane with its fuel that there wasn't much energy/fuel left to fly bombs anywhere."
VTOL an exaggerated and over-rated capability? Short-takeoff-landing [STOL] used most of the time? Those Harriers as used by the British during the Falkland Islands/Malvinas War for the most part not using VTOL? Those "jump jet" "ski-slope" light aircraft carriers more than sufficing for the role as intended, not as commodious as a super-carrier but still performing yeoman service, adequate.
Once more as to the STOL/VTOL problem, as stated by the acknowledged aviation authority:
"The Harriers worked fine. buy some of them, put on modern avionics and have at it!"
That F-35 decision to buy before you fly having been already made, an upgraded and improved Harrier is NOT an option, at least for the Marines?
"We don't have another option."