Notes: The difference between the S-64 and CH-54 is in the certification category of the two different models. The S-64 is a "standard category" aircraft. This is the most stringent, and therefore most expensive, certification to obtain from the FAA. All aircraft that carry passengers for hire or operate over populated/congested areas are required to be "standard category." In 1992, Erickson took over the Type Certificate for the S-64, making Erickson the manufacturer and sole support of all S-64's. All Aircranes operated by Erickson are standard category. The CH-54 is a "restricted category" aircraft. It was built for the military and was not originally subject to the FAA certification process until the military sold the aircraft as "surplus." For the CH-54 to be operated by civilian operators, who are subject to the FAA regulation, the FAA offers the "restricted category" certification. Restricted category aircraft are not allowed to operate over populated/congested areas, such as cities, nor are they allowed to carry passengers for hire. In some circumstances, restricted category aircraft can be operated just as safely as standard category aircraft, however, the maintenance and operating guidelines are more strict for standard category aircraft. Erickson does not provide parts or support for the CH-54, nor does any other company, including Sikorsky. This leaves the individual operators of the CH-54 to fend for themselves for parts and other support. Many CH-54 operators have purchased 5 or 6 surplus CH-54's just so than can keep 1 or 2 aircraft operating.

Courtsey of http://www.aviation-history.com/sikorsky/s64.htm

Also known as the Tarhe flying crane.