Delivered to United in July 1953 as N37568 "Mainliner Des Moines", it served until October 1968 when it had flown 32,296 hours. In December 1971 it was acquired by the Fairbanks-based Aero Retardant Inc. who converted it as a fire bomber, becoming Tanker 52 / D2. The following year it was transferred to the sister company Pacific Alaska Airlines, and operated until 1980 when it was sold to B&D Aircraft Inc. for parting out. After lingering at on at Chino for many years it was finally broken up c.1990, the nose section being noted at The Aviation Warehouse at El Mirage, CA. in October 1992.

The aircraft's original military serial was 42-16959. It came on to the US register in April 1984 as N46CM and has since been restored in WWII military colours, but retains the R-985 engine. Despite having an owner with a Northern California address, online photos suggest it is still Chino based, and it was recently tracked flying out of John Wayne Airport in nearby Orange County.

At the time of the photo it had been leased to The Doobie Brothers rock band and painted in a similar livery to their other M404s N467M and N3711K, but the registration harks back to the time it was operated for the country music band Danny Davis and the Nashville Brass. It was withdrawn from use in 1984 and donated to the George T. Baker Aviation School at Miami as an instructional airframe.

For sure one of the finest airliners ever built.

Used to carry the road crew, musical instruments and sound equipment of The Doobie Brothers Band when they were out on tour. The band themselves travelled in their small fleet of Martin 404s which were dubbed "Doobie Liners", hence this aircraft being dubbed "Crewbie Liner".

Scrapped at Hemet-Ryan c.1989. This registration is now carried by a USDA OV-10A Bronco.

EC2/12 aircraft at its home base. Later converted to F1CT.