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你是个不学无术之人， 要发新闻就好好研究再发， 否则不是蠢就是坏 A major cause for these delays was Lockheed Martin’s Technology Refresh 3 (TR-3), a US$1.9 billion package of hardware and software upgrades essential to the Block 4 modernisation.
However, given China’s near-total chokehold on rare earth elements, which are crucial for the F-35’s Block 4 upgrade, in the future, the F-35 deliveries can face further delays and cost overruns.
How China Can Delay F-35 Block 4 Upgrade
While the GAO report did not specify the reasons for the F-35 delays, according to some analysts, a significant reason could be China’s total control over rare earth elements and the restrictions Beijing has imposed on their exports to the US.
For instance, one planned upgrade under the Block 4 initiative involves a new radar system called AN/APG-85 that uses gallium nitride (GaN) antenna elements.

究竟谁是不学无术人？臆想还不如用数据说话。F35的产量一直在爬坡。看一下28楼网友回帖。