A relatively thin swept wing configuration was adopted after wartime aerodynamic research from Germany indicated its favourable high speed qualities.

Sweden had fallen behind the rapid technical progress being made elsewhere, and Saab needed to catch up in terms of aerodynamics and jet propulsion.

The first of these, codenamed R 101, nicknamed cigarren (the cigar) due to its shape, bore a strong resemblance to the American Lockheed P-80 Shooting Star.

SAAB's project manager, Frid Wänström, collected these documents in 1945 from Messerschmitt engineers who escaped to Switzerland at the end of the War.

These documents clearly indicated delta and swept-wing designs "reduc[e] drag dramatically as the aircraft approached the sound barrier.

[9][10] Wind tunnel testing at the Swedish Royal University of Technology and by the National Aeronautical Research Institute also influenced its aerodynamics.

[11] These tests determined the required fuselage form to ensure it could attain the targeted critical Mach number, as well as supporting the use of a straight-through airflow to maximize thrust.

[12] Automatically locking leading edge slots, interconnected with the flaps, were also deemed necessary for lateral stability during take-off and landing.

[10] Despite early doubts for the supply of an equivalent to the American 75S aluminium alloy, Svenska Metallverken was able to manufacture it, although significantly larger sections were used than typical for aircraft construction.

[14] The structure employed heavy frames and stressed skin to meet conflicting requirements on space, strength, rigidity and accessibility.

[15] Static testing of the full-scale mock-up revealed problems with pressure cabin leaks, and concerning aileron behavior.

[9] To improve pilot survivability, the Tunnan used an ejection seat Saab developed in 1943, with an explosive jettisoning system for the canopy.

[20] Improvements were made to the wing to incorporate a dog-tooth leading edge, raising the critical Mach number.

[21] The J 29 was fast and agile, and set the world speed record on a 500 km (310 mi) closed circuit in 1954[22] at 977 km/h (607.05 mph).

Two S 29C (reconnaissance variant) additionally set an international speed record of 900.6 km/h (559.4 mph) over a 1,000 km (620 mi) closed-circuit course in 1955.

[4][22] The crash record in early service was poor, mainly due to the inexperience with swept-winged aircraft and the lack of a two-seat, dual control Tunnan trainer variant: this meant that Swedish fighter pilots could only be trained using two seat variants of the de Havilland Vampire (a straight-winged jet), before going solo in a Tunnan.

[7] In May 1967, the fighter versions of the Tunnan was retired from combat service; however, a number of aircraft were retained and reconfigured for use as countermeasures trainers and for target towing duties into the 1970s.

[27] This second batch was modified so a camera pod could be installed in the port side of the nose of each aircraft, which required the removal of two cannons.

Swedish pilots refused some requests for close air support to ground troops, reasoning that the risk of civilian casualties was too high.

In November 1962, the Swedish air commander refused a direct order to destroy the secessionist's Fouga Magisters since they were unarmed.

When ONUC ended in 1964, some of the Swedish aircraft were deliberately destroyed at their base, as they were no longer needed in Sweden, having been superseded by later variants, and the cost of returning them wasn't justified.