The really big boom in general aviation wasn't the postwar years, but one that started in the 1970s. During this boom more than 10,000 airplanes per year were manufactured, building to a crescendo in 1979 when just short of 18,000 airplanes were delivered. Nobody in the industry or government predicted the onset of the boom, and it lasted long enough that no expert foretold the looming collapse that came in 1980. By the mid-80s the industry teetered on the brink of oblivion. Cessna, Beech, Learjet, Piper and Mooney were all purchased by large corporations as conditions made it virtually impossible for them to remain independent. Dozens of models went out of production, and manufacturers such as Aero Commander, Bellanca, Grumman American and others went out of the piston airplane building business.