They sure did, and were rewarded by having their company go out of business. A-10 was designed and built by the Fairchild-Republic. (I think that was the name at the time) Some of the support functions were taken over by Grumman for a while at least. Now I've lost track. I know (Northrop-)Gruman doesn't do the support work, I think Lockeed-Martin does. It wasn't the A-10 that did in Republic, it was a trainer, the T-46 Eaglet, aka the Thunder Piglet. Fairchild Industries was trying to sell Fairchild-Republic at the time the T-46 was being desinged, prototypes built and tested. Eventualy they just shut it down. Republic also designed a couple of other pretty rugged airplanes, the P-47 Thunderbolt of WW-II, for which the A-10 is named, and the F-105 Thundechief used extensively in Vietnam.