How Saab's Viggen Jet Fighter Locked Onto the US SR-71 Blackbird

The Viggen remains the only fighter to ever lock onto the SR-71. Thanks to knowing the patterns of SR-71 flight paths and sophisticated radar systems, the SR-71 would be locked onto by the Viggens multiple times, showing just how strong the Swedish fighter was, despite its speed disadvantage.

How the Saab Viggen was so capable

The Viggen was one of the most impressive fighter aircraft of the Cold War. The aircraft was Mach 2 capable, and Saab had created a jet that could take off and land in short field areas. In other words, from small temporary runways or even on autobahns and highways in Europe. Power came from a single Volvo RM8B afterburning turbofan, propelling the aircraft to a top speed of Mach 2.1 or 1,386 mph. The Viggen sports a delta wing design, with its main delta wing complemented by a smaller, high-set canard foreplane in front of it. This is a setup that has been applied to later aircraft like the Saab JAS 39 Gripen.

The Viggen would also utilize a sophisticated set of avionics. The American CD107 was a computer that featured in later versions of the Viggen, controlling all the various electronic equipment within the aircraft, like the earlier CK 37 computer. Ericsson radar systems would provide the eyes in the sky for the Swedish fighter and were used to good effect when Sweden intercepted the SR-71. Sweden knew letting the SR-71s fly uninterrupted through their airspace could impact national security. So a plan to intercept the SR-71 was formed.

How the Swedish Viggen would intercept the SR-71

The SR-71s ran missions through the “Baltic Express,” an area that saw the aircraft fly through a small gap of international airspace right by Sweden's controlled airspace. The plane triggered Swedish radar systems as they entered a way-point near Copenhagen. The Swedish pilots came up with a plan to intercept the SR-71. Rather than come from behind, the Viggens would enter a steep climb to just below the SR-71 and then accelerate to Mach 2. The aircraft would climb again, flying directly towards the American spy plane head-on.

This was like a game of chicken at Mach 2, and it made use of the radar in the Skyflash missile that the Viggen used. It was a risky strategy but the only one that would ever give the Swedish fighters a chance to lock onto the Blackbird. Doing so from behind would be impossible as the SR-71 would simply out-accelerate the Viggen. In January 1986, though, the plan to intercept the SR-71 would payoff thanks to Swedish pilot Per-Olof Eldh. This would be the first time an SR-71 was locked onto by an intercepting aircraft.

The Viggen finally intercepts the SR-71 Blackbird

An alert came through that an SR-71 was approaching Swedish airspace. So Eldh scrambled in his Viggen to try and intercept the American aircraft. He climbed as fast as he could before eventually reaching the altitude that the SR-71 was flying at. He started the head-on attack and lined himself up with the Blackbird. Then, Eldh managed to gain full missile lock on the SR-71 as it rapidly approached him, the missile fully armed and ready to fire. Naturally, the Swedish pilot wouldn’t fire, and the two aircraft passed by one another, with visual contact, also gained.

But the intercept had proven one thing. The SR-71 wasn't invincible. While none were ever shot down by the Soviet Union, the Swedish would lock onto the SR-71 several times. Eldh himself would do so another five times. To this day, the Saab 37 Viggen is the only aircraft to lock onto the Blackbird successfully.

The Viggen had earned its retirement

The Viggen would serve with the Swedish Air Force in its various forms from the early 1970s and right up until 2007. The retirement of the aircraft would begin in 1994, as the JAS 39 Gripen was gradually phased into Swedish service. The last front line Viggen would be retired on November 25, 2005, while a few examples would fly on. These for electronic warfare training against the Gripen.

The last of those Vigens would fly in June 2007, bringing the curtain down on the aircraft's legendary career. Having intercepted the world's fastest spy aircraft, the Viggen had certainly earned its retirement. It remains one of the most capable aircraft of the Cold War.