This paper reports a propulsion motor for a solar-powered aircraft. The motor uses precompressed aluminum stator windings, with a fill factor of greater than 75%, in a permanent magnet synchronous machine. The motor performance is compared empirically to an identical machine with conventionally wound copper windings. It is shown that there are many advantages to using compressed aluminum windings in terms of weight reduction, thermal improvement, and lower cost, for the same loss and electromagnetic performance, provided a sufficiently high slot fill factor can be achieved. The design and manufacture of the compressed coils is also discussed. A modular stator arrangement is used, in the form of a solid coreback with keyed teeth to allow easy assembly of the compressed windings. It is noted that the electromagnetic performance of the machine is unaffected by the modular nature of the magnetic core. Two prototype motors, one wound with conventional copper and the other with precompressed aluminum windings, are constructed and tested.