The Waco UPF-7 is an unusual airplane. This is not due to any outstanding technical features but to timing. A relatively obsolete design, it was built in quantity at a time when the open cockpit biplane trainer for civilian use was virtually extinct. Even then, it slipped into service unnoticed since it had no significant new features to arouse the interest of the contemporary aviation press.

Production of commercial biplane trainers virtually ended in Depression years of the early 1930s, and new low-powered monoplanes rapidly took their place in the schools and in private aviation. Only the Army and Navy were principal customers for biplane trainers in succeeding years. While Waco did not have a share of this market, it was one of the few firms that continued to supply open cockpit biplanes to private owners of the mid-1930s, a group comprising what could be considered a custom trade. Yet the UPF-7, introduced in the late twilight of the biplane era, was built in greater quantity than any single Waco model that preceded it. Approximately 600 came out of the Troy, Ohio factory between 1937 and 1942.

The reason for the volume production was inherent in the times. The imminence of World War II had shaken the government into expansion of the armed forces, including their air arms. While more cadets were trained by the services, and more biplane trainers were produced, Waco still did not obtain any significant military trainer business

The UPF-7 was a continuation of the Waco "F" series which had been introduced with Model INF of 1930, a three-seater powered with a 100 hp Kinner K-5 engine. Other Fs in the series used a variety of engines up to 220 hp. The UPF-7 standardized on the 220 hp Continental W-670-6A, civil equivalent of Continental's R-670 military engine.

Its designation reflected the principal design characteristics of the airplane - - the letter "U" identified the engine as the W-670, the "P" identified the wing and fuselage design, the "F" identified the model type or series. Details like landing gear and tail shape varied greatly through the series. While the UPF-7 was built in the largest numbers, there were limited other versions also built, mostly for special customers. These were known as LPF, VPF, YPF, and ZPF models. The only difference being the installation of different engines.

Essentially a state-of-the-art refinement of the 1930 model, the UPF-7 retained its major features, particularly the heavily staggered wings with the strut-connected ailerons in upper and lower panels. The earlier Fs were all built as three-seaters, with two passengers seated side-by-side in the front cockpit. The UPF-7 was intended to be a dual-control trainer, but when the stick was removed, the front seat was wide enough to accommodate two passengers.

Significant private ownership of UPF-7s did not occur until late in WWII, when some of the training schools were phased out. The government bought a number of the unemployed UPF-7s for the surviving schools, but others found new civil owners, particularly crop dusters that were hungry for replacement airplanes in a nation geared to military production. After the war, the UPF-7s did not have any particular appeal to non-commercial owners; they were just cheap old airplanes, good for time building by pilots who flew them for little more than the cost of fuel. More then ended up in the dusting business, which at the time operated almost exclusively with obsolete airplanes. A few, thanks to their low cost and good cooling of the radial engine, found homes in glider clubs where they made fine tow-planes. Although used for aerobatics training, the UPF-7 could not match the Stearman/Boeing "Kaydet" at air show work and so did not find a new career in that field.

The birth of the antique airplane boom in the 1950s gave the venerable Waco UPF-7 a new lease on life. Many worn-out hulks that had been out of license for years, plus a good number of junked "basket cases" were rescued from their positions in the weeds behind the hangar, lovingly restored, and put back in the air by new owners. Others became available to the Antiquer’s when new designed-for-the-purpose monoplane dusters forced more and more of the old biplane conversions out of the agricultural fleet. These were relatively easy to convert back to "two-holers" for the helmet-and-goggles set.

In addition to the current nostalgic hobby activities, some UPF-7s are back in commercial operation at schools that teach aerobatics while others, thanks to two-seat front cockpits, hop paying passengers at air shows. Some are used for barnstorming in search of passengers.

As is customary with hobby airplanes, many of the UPF-7s have undergone considerable modification at the hands of the Antiquer’s. However, they stay within the limitations of their standard licenses. While Waco was famous for the high-quality finish on some of its custom models of the 1930s, no UPF-7 ever left the factory with the quality of finish applied by some of the Antiquer’s of today - 24 coat hand-rubbed dope jobs, chromed metal parts, arty paint jobs and metallic tape striping and lettering. The most common modification is the addition of a full cowling around the engine, as used by the PT-14s and the use of wheel pants.

An oddity of the antique boom was the popularity of the colourful pre-WWII Army paint job and markings for those airplane models that could have used them. Thanks to a few PT-14s, the UPF-7 qualifies for these legitimately.

Of course, many of these have minor goofs in the placement of proportions of the markings, but the spirit is there. The most common error is to make the vertical blue rudder strip too narrow (it should be one-third the maximum chord of the rudder), No one has carried marking accuracy so far, however, as to reproduce a major error committed in the Waco paint shop. The wing stars on all PT-14s were way out of proportion, an error Waco repeated on its prototype Army gliders, the XCG-3 and XCG-4.

From the original 600, the total of Waco UPF-7s has decreased steadily. Today there are more than 150 registered.