There's a whole new online site to answer all of your BushAWOL questions:

Under Air Force policy in force at that time, the only way that someone in Bush’s position could be placed in an “Inactive Status” was if they were being “completely severed from military status.” And the only way that could happen is if someone had become permanently disabled, or deserted. Bush was not disabled.

Instead, consistent with contemporaneous laws, regulations, and procedures, ARPC had reviewed Bush’s records, and found that he had failed to “satisfactorily participate” as a member of TXANG. Bush was then ordered to active duty, for which he did not show up. ARPC then certified him for immediate induction as a “non-locatee” (e.g. a deserter) through the Selective Service System.

This is the only explanation that is consistent with Bush’s military records and Air Force policy of that era.

~snip~

Sometime after this order was mailed, George W. Bush finally communicated with the Air Force Reserves. In an undated letter, he requests information on how to get out of the “Standby Reserves” in order to make absolutely certain that even in the case of the most dire national emergency, when the USA needs the services of even those who are on the “Inactive Status” list, George W. Bush would not be called to serve his country.

Bush even includes a mailing address, to make sure that he finds out how to avoid any possibility of service as soon as possible.

Oh and here's our valiant AWOL-in-Chief when he actually did show up for duty: