When I started at LASI at KIDL in 1954, one of our customers was Aramco. I must say, their DC-4 and DC-6 were the most immaculately maintained aircraft, almost equal to the US SAMFLEET planes. They pulled out not long after I started.
The one outstanding feature I remember on the DC-4 were the aft toilets. No tanks to catch waste. Simply a stainless steel tube leading directly overboard. On the lavatory doors were instructions not to use the toilet over populated land. Best toilet system I ever saw and the easiest to maintain. .