When you see them at airports, you probably don't give them a second thought. Cessna aircraft are very common and are, typically, privately owned. But what you may not know is that the United States military — and a fair number of allies — used basic Cessnas for nearly a quarter-century. In fact, these planes saw service in both the Korean War and the Vietnam War.
Now, the Department of Defense didn't call them Cessnas. Their official designation was the L-19 (later the O-1) Bird Dog. The Army ordered this plane in the wake of the 1947 divorce with the Air Force (and the establishment of the 1948 Key West Agreement). At the time, the Army was looking for a scout plane that could also serve as an artillery spotter.
The Cessna design was slated for introduction in December, 1950. Just six months before then, the Korean War broke out — and the artillery spotter, though effective in its primary mission, quickly proved capable of much more, handing a variety of missions ranging from medical evacuations to general liaison.
The Army and Marine Corps bought over 3,200 of these planes. While the planes proved useful in Korea, it was in Vietnam that they would become legends. There, the Bird Dogs were used by forward air controllers, or FACs, to accurately spot for close-air support. The jets bringing that support to troops on the ground were very fast. Without the guidance provided by the Bird Dogs (who had a much more clear view), they stood a greater chance of missing the intended target — in the worst cases, this resulted in landing air strikes on American troops.
In Vietnam, the Bird Dog also acquired some armament in the form of rocket pods. These weren't to attack enemy forces, but instead served as a means to mark targets for jets carrying the heavy firepower. Over 500 Bird Dogs were lost in Vietnam.
In 1974, the Air Force retired this plane, but it was passed down to other countries, including South Vietnam.