The GE powered M11s were leased from MD until the Pratt powered ones recieved certification. Delta operated only 2 or 3 of them, and while they filled the void of having no M11s, they also served for crew traning, and saw mostly ATL-Florida and transcon routes.
Two of Delta's first M11s were in fact GE-powered (453/454). Those aircraft were leased from Tombo Aviation, and eventually went to VASP. After that, the DL fleet was delivered with PW4460 engines. Both aircraft have been converted to freighters and are currently flying for Gemini Air Cargo.
N891DL and N892DL were originally ordered (but never operated) by Air Europe as G-MDII and G-OLAN. They were operated in their 10-abreast coach configuration for a couple of years (later changed to 9 across) on the MCO-LAX-NRT route.
This plane is built to withstand anything... except a bad pilot.