It's the price tag.
Here's What You Need to Remember: Britain might be able to pull off creating a powerful new stealth fighter, but the price tag might mean London will have to cut purchases of the American-made F-35 stealth jet.
The United Kingdom is forging ahead with its ambitious project to produce a home-grown stealth warplane, even as it strives to retain its status as one of the core partners in the F-35 stealth fighter jet program.
London is doubling down on plans to indigenously produce its upcoming BAE Systems Tempest jet fighter, a next-generation successor to the United Kingdom’s Eurofighter Typhoon fleet. In a March 2021 Command Paper to Parliament, the British Ministry of Defense (MOD) reiterated that the Tempest fighter will be a major procurement priority into the coming decades. “Tempest will exploit our unique industrial base to create a 6th generation combat air enterprise centred in the UK,” the paper reads. “This fully digital enterprise will transform delivery, achieving pace and lowering cost and disrupting traditional approaches to defence procurement.”