This Beech 18 is one of the 31 aircraft on display all around the Lackland parade field. It is incorrectly painted as USAF 42-9637 (which was a P-39N), but it never served with the USAF. The serial is correct for this aircraft, but it's a US Navy bureau number, not a USAF tail number. This aircraft is in fact the USN BuNo 29637, first delivered as such as an SNB-2C in Oct 1944. Converted to SNB-3 in Jan 1949, then to SNB-5 in Dec 1951. Redesignated to TC-45J in Sep 1962 and to UC-45J in Oct 1964. In Feb 1967 it went to the US Army, where it served with that same serial 29637. At the time of the photo the Beech was receiving some TLC, hence the stepladder behind.

Aircraft is painted as Air Force 42-9637 which was actually a P-39N. Actual identity is the very convient USN BuNo 29637.