02/28/2011. Remarks by Johan Visschedijk: "In the mid-1950s the KLM had a need for a larger aircraft with longer range than the Viscount, and on February 29, 1956, twelve Model 188As were ordered. Subsequently the type ordered was altered into Model 188C, which had a longer range with increased fuel tankage, 6,490 gal (24,567 l) versus 5,450 gal (20,631 l) and higher take off weight, 116,000 lb (52,617 kg) versus 113,000 lb (51,256 kg).

The twelve KLM 188Cs had the c/n 2001, 2003, 2006, 2009, 2012 to 2019, and the registrations PH-LLA to PH-LLM (minus PH-LLJ), however, the first aircraft was initially registered to Lockheed as N6934C, flown June 6, 1959, it was delivered to KLM on September 21, registered PH-LLA and named Mercurius (Mercury). Nine years later, March 18, 1968, the aircraft was sold to Universal Airlines of the USA, and it was stricken from the Dutch register on March 23.

Registered N851U the aircraft was converted by the Lockheed Aircraft Service Company into a Model 188C(F) freighter, and as such it started operations on September 20, 1969. On March 19, 1972, while landing at Hill AFB, Utah, the aircraft suffered a propeller separation, resulting in a major fire, and the aircraft was damaged beyond repair. The front part (some 40%) was used by California Airmotive to construct a 'new' aircraft, using the rear part (some 60%) of N33506 c/n 2010. The 'new' Model 188PF got the c/n 2010 and was registered N33506."