The Lockheed A-28 was the USAAF designation for Pratt & Whitney powered Lockheed Hudsons, introduced under the terms of the lend-lease act. All military equipment provided under lend-lease had officially to be on the books of the American military, and so required an official designation. The Hudson would eventually be give two USAAF designations – A-28 for aircraft powered by Pratt & Whitney R-1830 engines and A-29 for aircraft powered by Wright R-1820 engines. While a significant number of A-29s were retained by the USAAF, the same was not the case for the A-28.
The A-28 was produced in two versions. The A-28-LO was similar to the Mk IV, and was powered by the Pratt & Whitney R-1830-45 (the military designation for the engine used in the Mk IV). Fifty two were built, all of which served with the RAAF as the Hudson Mk IVA.
The A-28A-LO was powered by the more powerful 1,200hp R-1830-67 engine. It was similar to the Hudson Mk V, but with an interior that could easily be converted from carrying bombs to carrying troops. A total of 450 were built, of which 410 went to the RAF, 36 to the RCAF and four to the RNZAF, where they served as the Hudson Mk.VI. One aircraft went to Portugal, and at least three of the RAF aircraft were returned to the USAAF, making them the only A-28s to enter American service.