Yuk-28P

The Soviets loved adapting airframes to new missions, almost as much as they loved developing new weapon systems. I don't just mean radars and missiles, but entire sets of computers and datalinks. This is why they built so many planes for ostensibly one single purpose. The Yak-28P offered something the Soviet PVO didn't have in the early 1960s, though: the combination of supersonic performance, long range, and the space for a radar operator. The Tu-128 would offer even more range and the Mig-31 would surpass both, but the Yak-28P stayed in service until 1988, until finally they were replaced with the Su-27P. Talk about an upgrade!