On this date in 1961, a jet designed for commercial use became the first civilian craft to go supersonic. It wasn't the famous Concorde, which wouldn't break the sound barrier until an October '69 test flight, or the Soviet-built Tupolev Tu-144, but rather a humble DC-8—no. N9604Z, to be specific.

It was all part of an August 21, 1961 test flight from Edwards Air Force Base thought up by Douglas pilot William Magruder. According to flight test engineer Richard Edwards, who spoke with Air & Space Magazine, the idea was to "get it out there, show the airplane can survive this and not fall apart." At the time, DC-8s had been used by commercial carriers for about three years and were competing with the Boeing 707. While DC-8s weren't designed to go supersonic, the bragging rights of being the first to do so were worth making the attempt.

In order to reach Mach 1, the jet had to be in a dive. This meant taking it up to 52,000 feet, which was also a record for altitude. As Edwards tells Air & Space Magazine:

We took it up to 10 miles up...and put it in a half-a-G pushover. Bill maintained about 50 pounds of push. He didn’t trim it for the dive so that it would want to pull out by itself. In the dive, at about 45,000 feet, it went to Mach 1.01 for maybe 16 seconds, then he recovered. But the recovery was a little scary.

The stabilizer was overloaded and the plane stalled when Magruder tried to pull it back. "What he did, because he was smart, is something that no other pilot would do," says Edwards. "He pushed over into the dive more, which relieved the load on the stabilizer. He was able to run the [stabilizer] motor...and he recovered at about 35,000 feet." The crew successfully turned a mass-produced airliner into the world's supersonic commuter jet. (Right by their side the entire time? Chuck Yeager, the first person to ever go supersonic in 1947. He escorted the DC-8 during its test in an F-104.)

"That’s an unofficial supersonic record, payload record, and of course an altitude record for a commercial transport," says Edwards.

After the test, DC-8 no. N9604Z was delivered to Canadian Pacific Air Lines and was used by the carrier for almost two decades before being retired. But this piece of aviation history isn't hanging in a museum somewhere. After it was put out of service, Canadian Pacific sold DC-8 no. N9604Z for scrap. That's some pretty fast junk.

[Sources: Air & Space Magazine, NYCAviation; Image above is a Canadian Pacific DC-8, albeit not no. N9604Z]