By the early 1960s, company leaders realized they didn’t have the right entry for a growing compact sports car segment led by the Chevrolet Corvair Monza. The Ford Falcon Futura, even with a Thunderbird-style roof, along with other specialty Falcon models, didn’t have the goods to compete.

Recently, a trove of early planning documents for what became the Ford Mustang – then known as Special Falcon – was published by the Ford archives team. This includes notes from a series of weekly review meetings that took place in 1962 and 1963, along with other insightful internal memos. One particularly notable revelation is the fact that a revised Thunderbird concept on the Falcon chassis – dubbed XT-Bird – was initially considered before Special Falcon won out.

The nascent compact sports car market accounted for more than 500,000 units of sales in 1962, with Ford claiming just 12 percent of the segment, well below its overall share. Ford’s deficit accounted for “a sizable portion of our outsold condition,” and company leaders knew having a competitive entry in the segment would enable Ford to get a foothold with younger buyers.

“We believe the company needs an exciting new product of this type to stimulate interest in the Ford Motor Company and to restore a favorable image with the younger population,” Ford division vice president and general manager Lee Iacocca wrote in one July 1962 memo.

Competing in the compact sports car segment was so critical that Ford leaders were even prepared to revisit the XT-Bird concept if Special Falcon proved unsuccessful.

Another impetus for the new car was the fact that General Motors, already dominating the growing segment, was expected to introduce a challenger to Thunderbird, which had enjoyed a five-year stretch with little competition. Along with the arrival of Buick Riviera in 1963, GM was also expected to launch a new Chevrolet Corvette and Pontiac Grand Prix.

“It is proposed the company take similarly aggressive action to counter Monza,” another Ford executive wrote. Division leaders studied “a number of types of sporty cars,” including Ford’s own Fairlane and Thunderbird, and analyzed market conditions for alternative models. They ultimately decided an affordable new four-seater with “attractive and unique” styling and six- and eight-cylinder engine options was needed.

The Special Falcon derivative would utilize its predecessor’s powertrain and chassis components wherever possible. The interchangeability helped keep production costs low, while offering improvements from specialty Falcon models introduced in the years prior – notably ride and exhaust restrictions. Special Falcon was expected to have better handling and those fun-to-drive characteristics customers were demanding.

The new car would be the same length as Falcon, slightly narrower, and two inches lower. In many aspects, its dimensions were similar to Monza – with the exception of a much longer hood and shorter deck, which is now synonymous with Mustang. Combined with the car’s lower height and the Falcon’s width, it had a “unique, sporty appearance,” according to internal documents.

While Special Falcon was benchmarked closely with Falcon and Monza, its design would include styling unique to the Ford Division, such as curved side glass, body-side turn-under and slim floating bumpers. It was not to look “Monza-ish,” according to the July 1962 memo, which stated, “We are not overly successful when we imitate GM, nor should the size and style of the vehicle increase and become Thunderbird-ish because of the substitution dangers.” The car was expected to offer a V8 engine that outperformed anything Ford or Chevrolet was running at the time.

Special Falcon, a name still unresolved after the more than 20 weekly meetings recapped in the documents, was projected to sell 150,000 units per year. Of course, it sold much better than anyone expected – more than 418,000 units in the first year alone. The car went on to sell more than 10 million units, becoming the world’s best-selling sports car several years running.

The project followed an aggressive timeline, going from an approved clay model to Job One in 18 months – 2.5 months faster than usual – a pace enabled in part by its commonality with Falcon. Mustang was revealed to the public at the World’s Fair on April 17, 1964 – a day we now celebrate as Mustang Day.