https://www.defensenews.com/smr/air-...to-beat-china/
"Kelly’s comments may portend that the program is at a turning point where more funding is needed to accelerate its development and fielding timeline. Lawmakers have been somewhat tepid to the program thus far, funding $904 million of the Air Force’s $1.044 billion request in fiscal 2021. The service previously received $905 million for the program in FY20."
If you take an aircraft fleet that is generally very cash-consumptive in the latter half of its (long) lifes, and progressively replace it with an aircraft fleet that is generally very cash-consumptive in the early years of its (short) lives, you get the mother of all cash squeezes during the transition.
It is no wonder that,
"In the FY21 defense policy bill, Congress also mandated that the Pentagon’s independent Cost Assessment and Program Evaluation office conduct a study on Air Force and Navy future fighter programs, including on NGAD’s technology, cost and business case."