<p>By 1941 the USAAC had firmly established the use of lightplanes for liaison and communications duties for army units. Among the types under evaluation for military purposes was the Stinson Model 105 Voyager of 1939. In 1941 this type had been refined into the Model 10, available as either the 10-A with Franklin engine or 10-B with a Lycoming. Six 10-As, re-engined with 80-hp Continental O-170-1s, were procured by the US Army for evaluation purposes as the YO-54. Successful trials with these aircraft (41-143/41-148) resulted in a contract for the militarized O-62, which was later redesignated L-5 and named the Sentinel. This is described separately.
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<p>To supplement the military purchase of L-5s, the Army also impressed several civilian aircraft. Eight Model 105s (42-88666/42-88673) with 90-hp Franklin O-200-1 engines were acquired, initially designated AT-19A but subsequently known as L-9As. The AT-19B/L-9B designations covered 12 Model 10-As (42-94130, 42-94136, 42-97051, 42-97430, 42-97432, 42-97434, 42-107278, 42-107406/42-107410) with 90-hp Franklin 4AC-199-E3 engines.
