Bruckner and Junkin actually began designing aircraft in 1919 with a flawed plan for a floating airplane that never flew. Meyers, too, had already designed an aircraft with Weaver and the pair approached Bruckner and Junkin, asking them to join their construction efforts on a single-seat monoplane named the “Cootie.” Unfortunately, Weaver crash-landed the Cootie during its first flight attempt and suffered extensive injuries in the crash. 

The WACO partners persevered, designing a practical three-seat biplane, the WACO 4, and building it out of parts left over from the Cootie and other biplane efforts. The team continued to assemble airplanes from parts salvaged from surplus World War I Curtiss Jennys, continuously tinkering with their designs and making improvements. Eventually, they sold two WACO 5 biplanes. 

Weaver Aircraft moved to Troy, Ohio, in 1923 and the company name was changed to the Advance Aircraft Company although the aircraft retained the WACO designation. The company became a pioneer in the development of reasonably priced, easy-to-fly small aircraft and the first Troy-built model in a long line of WACO aircraft, the WACO 6, was soon being marketed.  

The next aircraft design, the three-passenger WACO 7, powered by a Curtiss OX-5 engine, was modestly successful with 16 aircraft sold. In 1924, the first cabin WACO aircraft was manufactured, the six-passenger WACO 8, featuring an open cockpit positioned behind the cabin for the pilot and co-pilot. Only one WACO 8 was ever sold and it was eventually used to aerially map the Ozarks. 

Following Buck Weaver's death in 1924, Clayt Bruckner and Sam Junkin reorganized the business and soon introduced the company's popular Model 9 (or Nine) in 1925. Powered by a Curtiss OX-5 or Wright Hispano engine, the WACO Nine delivered better performance than the readily available war surplus Curtiss Jennys at a affordable price.  

The design of the Nine was state-of-the-art for its time—a fabric-covered wooden wing structure strengthened with welded steel tubing. The front cockpit was equipped with a bench seat that accommodated two passengers with a single cockpit for the pilot in the rear of the aircraft. An engine radiator mounted under the forward edge of the upper wing became a distinguishing WACO trait.  

The stylish WACO Nine made a good showing during the 1925 Ford Air Tour. The accompanying publicity quickly translated into increased aircraft sales and 276 Nines were sold between 1925 and 1927. An outstanding barnstormer, more than 14 Nines competed in the 1926 National Air Races with several finishing first in their events. WACO Nines also saw duty as crop-dusters—the airplane could be outfitted with floats for water landing—and were also used as an early commuter aircraft.  

The improved WACO Model 10 replaced the Nine in 1927, featuring a larger wing area, bigger cockpit, an adjustable stabilizer, and the first shock absorber landing gear built into a small aircraft. The WACO 10's performance was markedly enhanced and the aircraft was sold with several different engine options (OX-5, OXX-6, Hispano-Suiza and Wright J-5 Whirlwind). 

Noted for quick and straightforward takeoffs, a speedy rate of climb and equally tolerable landing speeds, the WACO 10's performance soon made it the most popular small aircraft in the United States. By 1927, more than 40 percent of small aircraft sold in the country were WACOs, including 350 WACO 10s at a sticker price of $2,460 (with the OX-5 engine). The WACO 10's reputation extended to the air race circuit as well: an OX-5 engine-powered model won the 1927 New York to Spokane, Washington, transcontinental Air Derby (Class B) and a Wright J-5-powered WACO 10 won the National Air Tour the following year. 

Advance Aircraft went on to manufacture the notable WACO Taperwing in 1928 and then, in 1929, the company officially renamed itself the WACO Aircraft Corporation to correspond with its now-famous line of aircraft. In 1931, WACO entered the burgeoning business aircraft market by introducing its four-passenger “QDC” cabin biplane to compete with such established manufacturers as Bellanca and Stinson. 

The QDC label marked the 1930 introduction of a cryptographic system of model designation that WACO used to identify its various models. The first letter identified the engine-type, the second the wing style, and the third the fuselage design. Each letter also indicated if the aircraft was built before or after 1930—a very confusing conglomeration of letters that required a scorecard to decipher. 

WACO replaced the QDC in 1933 with its most successful cabin design—the UIC. Powered by a 210-horsepower Continental radial engine, the UIC was a four-person biplane with a conventional fixed tail wheel landing gear. The well-appointed cabin was accessed by automobile-style doors on each side, with a pair of individual front seats and a roomy rear bench seat for another two passengers. 

The UIC's fabric-covered fuselage was constructed from welded steel tubing, shaped with wooden formers and stringers while the wings were fabricated with spruce spars, spruce and wooden ribs, and aluminium edges. Ailerons on both wings were covered in aluminium and connected with push-pull struts that operated them in pairs. The UIC's stable handling characteristics were considered to be forgiving, with good performance. Delivered with a full set of flight controls and instrumentation, the UIC was priced at a modest $6,000—well within the reach of smaller corporations and airlines.  

WACO delivered 83 UICs before replacing the model with the UKC/YKC/CJC series of cabin aircraft in 1934. These trendy airplanes became a favourite of aviators like Jacqueline Cochran and corporate magnates such as Henry Dupont. 

WACO continued to refine the aircraft design and accessories on an annual basis, but retained the basic configuration to maintain quality and avoid the high costs of wholesale redesign; as a result, selling prices remained stable and affordable. 

Production of WACO civil aircraft was suspended in 1942 after U.S. entry into World War II. The company contributed to the war effort by building assemblies for a variety of military aircraft and manufactured the well-known CG4-A troop-carrying gliders.