ANG pilots served in Vietnam from 1968 to 1970 through a volunteer program called "Palace Alert."
Palace Alert was an Air Force program that sent qualified F-102 pilots from the ANG to bases in Europe or southeast Asia for three to six months of frontline service.
This program was instituted because the Air Force lacked sufficient pilots of its own for duty in Vietnam but was unable to activate ANG units since Presidents Johnson and Nixon had decided not to do so for political reasons.
Thanks to Palace Alert, the Air Force was able to transfer much-needed National Guard pilots to Vietnam on a voluntary basis while not actually calling up their squadrons.
Fred Bradley, a friend of Bush's who was also serving in the Texas ANG, reported that he and Bush inquired about participating in Palace Alert.
However, the two were told by their flight instructor, Maj. Maurice Udell, that they were not yet qualified since they were still in training and did not have the 500 hours of flight experience required.
Furthermore, ANG veteran Col. William Campenni, who was a fellow pilot in the 111th FIS at the time, told the Washington Times that Palace Alert had stopped accepting new applicants before Bush would have been eligible.
Yeah - he just includes them among his most lucrative clients, lobbying on their behalf.