On this day in 1970, a British Dan-Air charter, flying a Comet 4 turbojet, crashes into the sea near Barcelona, Spain, killing 112 people.

The charter was commissioned by a tourist group who were headed for a summer vacation on the Spanish Mediterranean coast. The passengers boarded in the afternoon of July 3, the plane took off without incident and, as early evening approached, they neared their destination of Barcelona. The pilot called the air-traffic controller and indicated that they were 12 miles away and at 6,000 feet altitude.

This was the last anyone heard from the jet. No further contact was made to the air-traffic controllers. Witnesses in Mataro, Spain, spotted the plane going down. There were no survivors and the remains of the wreckage provided no clues as to the cause of the sudden crash. It remains a mystery.

The original Comet turbojet, built by De Havilland, was one of the first jet engines. It was used in the first scheduled flights between London and South Africa in 1952, and London and Tokyo the following year. It represented a major breakthrough in terms of air speed, cruising at nearly 500 miles per hour at 35,000 feet high. It could go almost 2,000 miles without refueling.

Immediately after the plane’s introduction, it was involved in serious accidents. In May 1953, a Comet aircraft disintegrated after leaving Calcutta, India. Fire took out another plane in mid-flight the following January. Then, just a few months later, yet another Comet went down over Rome. After that incident, all Comet aircrafts were temporarily removed from service; tests found that the Comet’s fuselage was subject to metal fatigue and cracking under the pressures of flight. An improved Comet was re-introduced in 1958, but fared poorly in competition with the newly introduced Boeing 707. It went out of production in 1968.