Chrome Dome missions were done with E & F models and that mission wore them out prematurely.
A bunch of F models ended up at Castle as trainers. "Worn out" is a good description! During a routine phase inspection a 10 foot long crack was discovered from the wing root going down the side of the fuselage on one plane. When they called Boeing to ask how to repair it, the answer was "Scrap it!" The wing commander had to ask for a volunteer crew to make one last flight to the boneyard at Davis-Monthan.
