On display at Steven F. Udvar-Hazy Center, National Air and Space Museum. This aircraft was originally built as an M-4 but later reconfigured as an M-2. The type was extensively used by Western Air Express to carry mail over the Contract Air Mail Route 4 (CAM-4) between Los Angeles and Salt Lake City. The M-2 could carry up to 1,000 pounds of mail in its forward compartment.
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