Instances?
I suppose its a bit like breathing. We get so used to it that we don't even notice after a while.
Comet, don't export it, but we will export the 707 (were that type of engine used on a long range bomber?)
Concorde, too loud for us. But we will build something bigger and faster (but failed)
There is another contender, but I'm not brave enough the mention THAT aircraft.