If a member was still in the AF in 1969 their service number whould change to their Social Security numbers. The Socical Security is now the service member identification.
Thanks! perhaps I did not explain my question clearly.
Robert Samuel Johnson (WWII UAAF ace) has a service number A000661217 in the book edited by Air Force Historical Research Agency in 1978 (https://www.afhra.af.mil/Portals/16/documents/Studies/51-100/AFD-090601-121.pdf). It has his SSN (https://aad.archives.gov/aad/display-partial-records.jsp?dt=3001&sc=29343%2C29348%2C29350%2C29353%2C29354%2C29355%2C2936… ). Not sure the Air Force Historical Research Agency book used which number. It is not the same number in the military enlistment records (illustrated by the case of Earl L Abbott above) and not SSN (as Robert S. Johnson case).
Dear Guohui Jiang,
Thank you for posting your request on History Hub!
It is possible that the discrepancy in service numbers stems from a change in an individual’s status from enlisted person to officer. The Access to Archival Databases (AAD) World War II Army Enlistment Records that you cited contains service numbers that were assigned when a person first enlisted in the Army, and the second document you cited seems to reflect promotions to higher ranks.
We suggest that you contact the US Army Center of Military History or the U.S. Army Heritage & Education Center for further assistance. Plus, you may find some useful information on this unofficial website titled How to Decode a WWII US Army Serial Number.
We hope this information is helpful. Best of luck with your research!