While only 58 were built, they served a wide variety of roles including private air yacht, airliner, military transport, and search and rescue.

The improved aircraft was named "Dolphin", however this did not represent the end of development, as many detail improvements were made, including an increase in the length of over a foot and changes made to the empennage, engine nacelles and wings.

[3] The Great Depression had curtailed demand for such extravagance as a "flying yacht", but Douglas managed to interest the United States Coast Guard who not only bought the Sinbad, but 12 Dolphins.

Subsequent examples were ordered by the United States Navy and U.S. Coast Guard for use as transports and search and rescue craft.

[7] Although never used by Roosevelt, this was the first aircraft procured to provide transportation for the President of the United States.