The biggest issue currently is how PPBE is structured. You can thank McNamara for the crappy architecture (PPBS) that leads to where we're at right now. The F15 came out of genuinely good combat fighter requirements in the late 60s. Radar auto-acquisition was a complete game changer. As time progressed through PPBS and into PPBE, timelines for purchases and life cycle became greater and it ultimately led to more industry consolidation. RAND did a pretty great study on the history of the fighter aircraft industry. What they found is that the greatest technological leaps forward happened when there was more competitors in the industry (no surprise to many here). IIRC, in the 50s there were 20+ primes competing with each other for post war money / survival. Right now there are two primes in the fighter business and only one company currently making operational air to air missiles. The F15's first flight was in 1972 - 51 years ago. To put that timeline into perspective, we went from fabric wing bi-planes to the SR-71 in approximately the same time. The key is competition. The business game plan of primes is usually to make competition a "risky" investment and drag out a contract as far as possible. The longer a single fighter contract drags out, the less capital staying power other businesses have to wait for the next big competition. The result is that they are typically bought out by whoever has the contract staying power. It's not always the case and there's a lot of roads that lead to consolidation - but the end result is that less businesses retain the technical and manufacturing prowess to actually produce a fighter. The only really way out of this is to take anti-trust action on the primes, break them all up while simultaneously changing the PPBE process and go to shorter term contracts with more competition intervals. It's impossible to predict combat requirements for a fighter or anticipate commercial technology developments 40 or 50 years into the future, so it's imperative to have a quick, iterative industry eco-system. That takes deliberate planning and knowing when to turn off a desperate deal, divest current fighters, etc.