The RB-1/C-93 was radical for its day, introducing many of the features now standard in military transports. The flight deck could accommodate three crew members, pilot and copilot side-by-side, the navigator behind them. Stairs connected the flight deck to the cargo area, which was 25 feet (7.6 m) long with an unobstructed cross-section of 8 × 8 feet (2.4m) throughout its length. Cargo loading and unloading could be accomplished in two ways: through 40 × 60 inch (102 × 152 cm) doors on both sides of the fuselage or by an electrically operated 10 × 8 foot (3.0 × 2.4 m) ramp at the aft end of the cargo area under the upswept tail, a similar development to what had been initially fitted to the Germans' own Ju 90 four-engined transport aircraft as their Trapoklappe ramp in 1939. The RB-1's loading ramp, accessed by manually operated clamshell doors, along with the tricycle landing gear, meant cargo could be loaded/unloaded at truck-bed height. A manually operated two-ton (907 kg) hoist for unloading trucks and a one-ton winch for pulling cargo up the ramp were also provided in the cargo area. The aircraft could accommodate:
- 24 paratroopers, or
- 24 stretchers and 16 sitting wounded, or
- 9,600 pounds of cargo, or
- a 1½ ton truck, or
- The largest ambulance in use by the U.S. military.
Production RB-1 aircraft never entered squadron service with the Navy, but a few were briefly used by Naval Air Stations as utility aircraft. With only 17 aircraft in inventory, the RB-1 was not feasible to maintain on the active list, and it was retired from U.S. Navy service in early 1945. The extant RB-1s were then transferred to the War Assets Administration (WAA) to be sold as war surplus. In 1945, the WAA sold 12 Conestogas to the National Skyway Freight Corp for $28,642 each at a time when new C-47s were selling for approximately $100,000 each. The new company, founded by members of the AVG Flying Tigers immediately sold four RB-1 aircraft to other buyers, which paid for the entire WAA contract.
The seven remaining National Skyways aircraft were used to transport a variety of cargo, shipping fruit and furniture from its base in Long Beach, California. [N 1] Pilots reported that the Budd transports were temperamental; in particular, exhaust stacks kept falling off and causing engine fires. There were three more crashes of Conestogas while in service with National Skyway Freight, one each in Virginia, New Mexico, and Michigan. [N 2] The crash in Virginia was a belly landing at a country club brought on by fuel exhaustion following weather-related problems. The Albuquerque, New Mexico crash was due to a downdraft during a snow storm, 80 miles (130 km) from Albuquerque.<Widow of Lawrence Molloy Feemster, Ruth Mae (Feemster) Hill & preserved newspaper clippings>[better source needed] Pilot and copilot were killed when they were thrown through the windshield and the aircraft skidded over them; the flight engineer survived.
In 1947, the U.S. Army (and later the U.S. Air Force) gave National Skyway Freight a large contract for trans-Pacific freight, for which it leased military aircraft. The company changed its name to Flying Tiger and replaced the RB-1s with C-47s for its U.S. freight routes; the RB-1s were sold off to other buyers. One of these aircraft, a prototype RB-1, "NC45354" was sold to the Tucker Motor Company to transport its demonstration 1948 Tucker Sedan to auto shows around the U.S.; it was reportedly later abandoned at an airfield in Oakland, California after repeated mechanical troubles.