The UK is to work closely with Italy and Japan to develop next-generation fighter jets, Prime Minister Rishi Sunak has announced.
The PM claimed the partnership will ensure the UK and allies are “outpacing and out-manoeuvring those who seek to do us harm”.
Downing Street says the Tempest will be in the air by 2035 and serve as a successor to the RAF Typhoon.
The ambition is for the planes developed under the global combat air programme (GCAP).
It will be enhanced by capabilities including uncrewed aircraft, advanced sensors and cutting-edge weaponry.
The Tempest is being developed amid fears UK air dominance is under threat.
The PM will launch the first major phase of the programme during a visit to RAF Coningsby, in Lincolnshire.
Ahead of the visit, he said: “The security of the United Kingdom, both today and for future generations, will always be of paramount importance to this government.
“That’s why we need to stay at the cutting-edge of advancements in defence technology – outpacing and out-manoeuvring those who seek to do us harm.
“The international partnership we have announced today with Italy and Japan aims to do just that, underlining that the security of the Euro-Atlantic and Indo-Pacific regions are indivisible.
“The next-generation of combat aircraft we design will protect us and our allies around the world by harnessing the strength of our world-beating defence industry – creating jobs while saving lives.”
The jet is expected to be able to fly faster than the speed of sound, and have the capability of firing hypersonic weapons in the future.