I'd heard this before but I couldn't relocate the source. Well, here it is again. Bush volunteered to go to Vietnam. Details here.

"The Air Force, in their ultimate wisdom, assembled a group of 102's and took them to Southeast Asia. Bush volunteered to go. But he needed to have 500 [flight] hours, but he only had just over 300 hours so he wasn't eligible to go,” Morrisey recalls.

Instapundit is on the case.