B52's were designed and built before the 1960s. They are still flying.
The other example is the F22. This jet is now 'obsolete' because parts cannot be obtained for it. F22's cannot be built anymore and some spare parts for the F22 cannot be obtained.
The USS John F Kennedy and USS Enterprise were both uniquely built CV and CVN's for the US Navy.
As was pointed out in the thread, if it costs over $1 billion for an 'oil change', then the ship should be scrapped.
On the other hand, the B52 is still in service and is a pretty good 'mule' for the US Air Force...
The B52 doesn’t sit in salt water, the manufacturer and suppliers are still around and they made so many that there are plenty of mothballed ones to snag parts off of if for some reason Boeing can’t come up with one. Due to how Boeing developed aircraft after the B-52, there’s plenty of airliner parts that can either be bolted on or be adapted to the plane to keep it flying.
The F22 is an artificial situation and not the Pentagon’s fault. The Obama administration took all the tooling and information ‘to preserve it’ as part of how they got approval of the program cancellation through Congress. And then it “mysteriously disappeared.” And we didn’t build enough of them to start.
Kennedy (CV-67) was the most expensive carrier in the fleet to maintain in 2005 with Enterprise being the second most expensive. It was originally supposed to be nuclear but they changed to conventional partway through construction, with all the problems that entails.