In the 1960s, Aero Union acquired five former US Navy AF-2 Guardians. Only two were fully converted to airtanker (N9995Z and N3144G), a third was partially converted, and two remained unused and unconverted. The latter three remained in storage at Chico, CA for many years.
Falsely painted as N9995Z, the Guardian at the Pima museum is in fact N9994Z, which was one of the unconverted aircraft. Aero Union donated it to the Pima Air Museum in 1991, restoring it to static display condition the previous year. Although this aircraft had never been an airtanker and had never seen service with Aero Union, they painted it in their full markings to resemble Aero Union's airtanker N9995Z / 21-E.

An early C-119, ex USAF 49-132. Transferred to MASDC on 7 Jan 1967, acquired by Aero Union in 1969, and converted to airtanker in Jun 1971, operating as Tanker #E21. The roof-mounted auxillary jet was fitted in May 1974. Sold to Hemet Valley Flying Service on 17 Mar 1975, now operating as Tanker #81. Withdrawn from use in 1987 and stored at Hemet Valley, CA. Transferred to the US Forest Service, then loaned to the Pima Air Museum in early 1992.

A very early Provider, converted in the 1960s from C-123B to C-123K (underwing jet pods, larger wheels). To MASDC on 5 Feb 1982 for a very brief stay, inventory code CP066. Acquired by TBM Inc. and registered to them as N3142D on 22 Jun 1982. Converted to airtanker in Feb 1984 as tanker #63, and painted in the markings seen here. Withdrawn from use in 1987, sold to Hemet Valley Flying Service in 1988, but not operated. Transferred to the US Forest Service in Oct 1989, then loaned to the Pima Air Museum in early 1990.