The F-35 program has had its problems, and more than a few of those were inflicted by the program architects themselves. at the same time, it's also suffering from the impacts of various congressional decisions along the way. The F-35 basically started out life as a replacement for the F-16. Historically we have maintained a small force of fast intercept fighters (p-51 mustangs, F-4 Phantom II's, F-15 strike eagle, F-22, etc) to protect our shorelines and deployed bases. That number is usually around 600 or so aircraft +/- repair units, spare parts, crashed airframes, what have you. The rest of the land fleet has typically been a less expensive, more numerous variant of aircraft of some sort, in the most recent case, the F-16. There are around 1,200 of those. There are another 600 various fighters floating around, including the ground attack units (250 A-10 warthogs,) trainers (another 200 or so), research aircraft, etc. The strike fighters are typically deployed in groups of 4 at a minimum to bases, usually with at least one spare bird for maintenance. So you need a certain number at a minimum just to replace our aging and failing F-15 fleet.
The problem is they didn't build enough F-22's to cover the entire F-15 fleet. Only about 200 of the 600 they needed. So, rather than building more, congress decided that the F-35 could fill that role. The F-35 was already too many replacement programs tacked into one program (the lift fan variant should have been a follow on design for example) trying to be a frontline fighter, but also a carrier based fighter, a harrier replacement for the marines, and an export grade fighter we could sell to our allies, which is the real reason the lift fan variant got pushed ahead so far. England and france wanted it.
The F-16 was a departure for jet designs at the time. Take the biggest fighter jet engine you can find at the time, and strap the smallest possible, most manouverable aircraft around that will still fit a human. Add a few hard points and some landing gear, and you have an F-16. only one engine, so it was fairly cheap compared to a twin engine F-15, build thousands of them so the price stayed low per aircraft, export a ton of them to our allies and hope they stay our allies, It was a formula that worked pretty well for the most part, and one they tried to repeat with the F-35. The F-35 is about the closest thing you will find to a stealth F-16, with the same strengths and weaknesses. the base aircraft and carrrier variants are fairly fast, manouverable, and can carry a large armament. They aren't as manouverable or as fast as the F-22, but they weren't meant to be. Had they just left it at a replacement for the F-16 the program would be on time, and under budget. When you throw the lift fan variant in the mix with the requirement to have comanality of parts throughout the airframe, then the redesigns to make the lift fan version work started impacting the cost per airframe of all the F-35s, including the export variants making them less attractive than other foreign competitors.
At the same time thats all going on, you have the Navy in mild revolt against the idea of making a single engine aircraft their primary fleet strike aircraft. So they decide to go with the F-18E super hornet, but never really pull out of the F-35 project. And there is good reason to not want a single engine aircraft anywhere near an aircraft carrier. Seawater and carrier landings are hard on engines. F-16's have a very nice engine, but they are notorious for engine failures. The F-35 will have that same problem due to the aperature size of the intake. There is a reason the F-16's nickname is the "Flying Lawn Dart" if that happens on land, you eject and the nice men in the fire truck come and pick you up. If you do that on an aircraft carrier takeoff, you get ran over by the aircraft carrier and then the sharks eat you. So anyways, that block of funding the F-35 team was kind of banking went elsewhere until congress mandated that the aircraft carriers would field a stealth aircraft of some sort.
Which brings us to the lift fan variant debacle. The lift fan units will account for maybe 200-300 of the 1,600 ish aircraft fleet including exports. those 300 aircraft have used around 60% of the entire program budget so far, making the cost per unit far higher than any of the partner development nations were expecting. At the same time we suckered England into selling their harriers early on military e-bay, and then we bought them all for our marines and put them back in service once we realized the F-35 was going to be delayed again.
At the same time this is all going on, the various drone programs finally start getting off the ground with performance features and payloads that make them useful for combat. Mainly due to advances in very small very accurate gyroscope technology from the cruise missile programs, but it finally became cheap and effective to field a reconisance aircraft with some combat capability and no pilot at risk. The pilot life support systems typically make up 20-30% of the weight of a fighter aircraft, so right away everyone starts seeing doller signs. A drone can go faster, climb higher, carry more weapons, and if it blows up, who cares, we have 40 more!
The problem for me, and what I think alot of people forget is the nature of the enemy we are likely to fight. It's either going to be china, or a resurgant russia. Either of them have advanced aircraft building capabilities, with plenty of pilots, airstrips and people to throw at them. They also both specalize in radio interference and EMP weapons, far more than even the U.S. ever has It is quite concievable that either of them could disrupt or outright disable a large number of drones. Those same scenarios wouldn't necessarily disable a human piloted aircraft. I suspect in the future we'll end up with drones paired with local piloted controll aircraft to intervene or reestablish control.
The most pressing reason to go ahead with the F-35 at this point is that the cost of maintaining or rebuilding all our existing aircraft would be much, much, much higher than the 500 billion remaining in the F-35 build budget. The cost of building a fleet of 1,200 x-47B's would also be way up there, and even if they did cancel the F-35 at this point, the cancellation costs would be enormous.
China has fielded a stealth fighter / bomber. it files, it is almost as stealthy as our birds, and given what they got from the tail of that stealth helicopter in pakistan and the crashed drone from Iran, they know everything we know about stealth aircraft coatings. They almost certanly have a strike fighter they haven't shown us yet too. So far their engine building techniques can't match the fuel cooled engines we are using in the F-22 and F-35, and probably won't for a decade or more, but they are closer than I feel comfortable with in most of the other aspects of their aircraft. Controlls its about a wash, avionics and sensors we have an edge, missiles we have a smaller edge, and we have alot of experianced pilots and excellent training programs.
I dunno . I like drones, and I can see where they have alot of utility, but we need piloted aircraft, even if only in a backup capacity for when the drones are neutralized Anything that relies on a teather back home of any sort to operate and function has a weakness. We also need more damned F-22's!
Besides, england and australia will probably declare war on us if we cancel the F-35 at this point.