The Viggen was named according to its shape, reminiscent of a bolt of lightning, which was particularly suitable since the first version was designed for ground attack.

Central computer and a secret weapon

The first SAAB AJ 37 Viggen was delivered to the Swedish Air Force in 1971. Because it contained a built-in computer, called the Central Calculator, a pilot could on his own manage all the various systems for which its predecessor, the A32 Lansen, required both a pilot and a back-seat navigator.

The aircraft could also to some extent be used as a fighter interceptor, but the main focus was ground attack, above all to attack Soviet landing craft and troop transports in the event of war. It could carry a wide range of weapons, including the top secret anti-ship 04 missile, said to be the most powerful airborne weapon used by Sweden, which could break a ship in half.

Interior image from the cockpit of an AJ37, the ground attack version of the Viggen.

Lower than anything else

Radar and other sensors also enabled the aitcraft to fly extremely low, somewhat of a specialty for Swedish ground attack operations. At a speed of over 1000 km/h as low as 30 feet above ground or sea level, the Viggen was now able to pose a threat that would be difficult to counter by any possible aggressor.

Even today it is difficult to be quick enough to detect and not least to hinder an aircraft that is able to attack in this way. The ground attack pilots of other countries were amazed when during exchange exercises they could experience Swedish ”mud moving” missions.

Thor, the God of thunder in ancient Norse mythology, who was said to travel around in a chariot pulled by two goats while he was throwing out lightning bolts, assisted by his hammer, called Mjölner, would definitely have appreciated this new ”Thunderbolt” and the way it was handled by Swedish Air Force pilots.

Hunters and trackers

However, even though the Viggen was first conceived as a ground attack aircraft, the concept of a multi-role aircraft was not dead. A 2-seat trainer version, the SK 37, a photographic reconnaissance version called the SF 37 and a maritime reconnaissance version, the SH 37, were produced and went into service, as replacements for the reconnaissance variants of the Lansen and Draken. Then it was the turn of the interceptor version, the JA 37, of which deliveries began in 1979.

The JA 37, also known as the Jaktviggen (Hunter Thunderbolt), differed from the earlier versions. It had a more powerful engine, the RM 8B, than the RM 8A. Installed in those. It also had a tremendous new Swedish-developed radar, Ericsson’s PS46-A, and more advanced electronics that could benefit from the increased capability of the new radar.

A duo of JA37 Viggens from F4 Air Wing in Östersund flying above a winter landscape.

The hunt for the Blackbird

Even though the Jaktviggen was not the fastest aircraft in the world, it was renowned for its ability to climb very quickly. The Jaktviggen is also one of the few aircraft that could get a radar lock on to the American spy aircraft, the SR-71 Blackbird, even though that aircraft was able to fly at Mach 3 and higher than almost any other aircraft.

On one occasion the outcome was dramatic. It was on 29 June 1987 that an SR-71 took off from Mildenhall iin Britain to carry out a routine spy flight around the Baltic Sea. There were not only Swedish Viggens that climbed to try to catch the ultra-fast and high spy aircraft, but also advanced fighters from the then Soviet Union and other countries in the Warsaw Pact, such as the then East Germany. However very few managed to complete an interception.

The SR-71 crews were always on their guard. It was still the Cold War and they were well aware that the Soviet Union was desperate to catch an SR-71 and find out about its top secret equipment. However the crews were certain that their speed, height and technology meant that they were relatively safe.

A retired SR-71 Blackbird on display outside a museum in the USA. Photo Peter Langsdale.

Accidents happen

However beyond the Baltic the worst happened. One of the SR-71’s engines failed, the aircraft lurched and and began to rapidly lose height. The pilot turned it towards Sweden and entered Swedish airspace over Gotland, all the time slowing down and descending. The invincible Blackbird had suffered deadly damage. The pilot and backseater now feared for their lives. They knew that Soviet tracking systems were watching every move and were now feverishly trying to make the most of this opportunity to send up fighters to catch them.

However the Swedish defences were also watching what was going on, and when they saw that a foreign aircraft was about to enter Swedish airspace they ordered two Swedish Viggens from 13 Air Wing at Norrköping to break off from a training exercise and intercept the intruder.

When the Swedish aircraft met up with the damaged spy aircraft they could immediately see that it was in dire trouble. Only one engine was working and the aircraft was continuously losing height. The SR-71 crew had set off an emergency transmitter that confirmed they had a severe problem. The Viggen pilots then decided to stay with the wounded aircraft and escort it in its struggle to reach Danish airspace.

A further problem arose; the Viggens were starting to run out of fuel. However another pair of Viggens had been launched so that they could relieve the original pair from 13 Wing. The new Viggens escorted the SR-71 as far as Denmark and safety, where by now it was at 12,000 feet altitude. Even so they succeeded via Denmark to reach an air base in West Germany and avoid a forced landing.

The saviours of the day

The American aircrew and their commanding officers were convinced that if the Viggens had not turned up and escorted the damaged aircraft it would probably have been shot down. Alternatively the Soviet Air Force could have forced it down on to territory controlled by the Soviets or the Warsaw Pact. Based in what was then East Germany were the USSR’s fastest aircraft, the MiG-25 Foxbat, which frequently attempted to intercept SR-71s on their routine reconnaissance missions over the Baltic.

Although Soviet fighters took off, the presence of the Viggens prevented them from trying to come close to the damaged SR-71.

Due to the Cold War and the need to avoid revealing too much about the SR-71’s secrets, this event was not revealed until long after the fall of the Soviet Union.

In November 2018 a ceremony was held in the American Embassy in Stockholm during which the four Viggen pilots were awarded the US Air Medal in thanks for their rapid and professional intervention to protect the damaged aircraft.

The two American aircrew were also convinced that the Viggen aircraft saved their lives.