I did business with O.B. and Max in the early 70s.  Traveled to Danang and Quang tri several times on their airline and also used their "charter cargo" services from time to time.  In the last two year or so before "liberation" I was one of the only Americans to have a tarmac pass that allowed me to drive across the runways between the military and civilian sides of Tan Son
Nhat (a little brown triangle on the windshield).  I still bump into people who remember my yellow pinto on the airstrip (there were 2 yellow pintos in Saigon.  There was never any question in local circles about the owner.  There were areas on the military side of the airfield considered super sensitive.  The VNAF were always having problems with ICCS observers attempting to gain access.  One afternoon I was stopped on the way out by a security guard.  He called his commander by handheld radio, and I distinctly heard him receive instructions to detain anyone in an ICCS jeep.  He turned to me to tell me that I was under arrest, and I asked him in Vietnamese whether my yellow pinto really looked like an ICCS jeep.  Then I drove out while he was standing there with his mouth open (maybe he was shocked that a round-eye would speak
to him with a Central Vietnamese accent).

I took trips in the AA Volpar from time to time and also shipped supplies out to Danang and Can Tho on AA aircraft (c123, c46, &C47).  My greatest challenge was to figure out how to fit cargo onto C47s and C46s without paying for the entire mission (my bosses didn't know how to spell "share," but the AA guys helped me.  My most memorable visit to the AA office in TSN
came in late 74 or early 75, when I was charged with arranging to fly a funeral group (including body in casket) up to Pleiku.  When our aircraft (I think it was a C123) arrived at Tan Son Nhat, however, it had on board a very large generator brought down from Pleiku or Danang.  The generator was too large for the AA forklift.  So we couldn't load our group.  The tarmac was very hot, which didn't improve the smell of the casket, and we were in near panic about how to unload the generator.  The pilot actually volunteered to take off and jettison cargo in the air, but I finally managed to sweet-talk some Vietnamese Air Force guys into lending us their super forklift, and we were able to get the deceased and the bereaved out of town before the casket became a public health menace.