The 747 is only one example. Martin Marietta made and launched Titan space launch vehicles from the early 60s to the early 90s, with only very slight changes and improvements. GD did much the same with the Atlas launch vehicle, and the Centaur upper stage. I will grant that NASA and Douglas&#x2F;McDonnel Douglas made a lot out of the Thor IRBM, but that seems like a function of NASA Administrators having longer tenure than anything else.