[4][5] As a reward, designer Alexander Yakovlev was awarded the Order of Lenin (Russian: Орден Ленина, Orden Lenina) (the highest civilian decoration bestowed by the Soviet Union), a 100,000 ruble prize, and a ZIS motor car.

The investigation of the crash found that the pilot had performed two consecutive barrel rolls at low altitude, which was in violation of the test flight plan.

It has been speculated that Piontkovskiy's deviation from the flight plan was caused by frustration that his aircraft was being used for engine testing while I-26-2, built with the lessons of I-26-1 in mind, was already performing aerobatics.

Technical problems with sub-assemblies provided by different suppliers raised the I-26-2's weight 400 kg (880 lb) above projected figures, which restricted the airframe to only 4.4 G, while oil overheating continued to occur.

Troublesome and slow testing and development concerned Soviet officials, since I-26 was ordered into production under the name "Yak-1" on 19 February 1940, a mere month after I-26-1 made its maiden flight.

Due to Operation Barbarossa the Axis invasion of the Soviet Union on 22 June 1941, development of promising designs, like the Polikarpov I-185, proved unfeasible.

The LaGG-3 experienced a significant degradation in performance (as much as 100 km/h (62 mph) on some aircraft) compared to its prototypes due to the manufacturer's inexperience with its special wooden construction, which suffered from warping and rotting when exposed to the elements.

[8] The M-105 could not tolerate negative G forces which starved it of fuel and suffered from breakdowns of magnetos, speed governors and emitted oil from the reduction shaft.

[8] A simulated combat between a Yak (with M-105PF engine) and a Bf 109F revealed that the Messerschmitt had only marginally superior maneuverability at 1,000 m (3,300 ft), though the German fighter could gain substantial advantage over the Yak-1 within four or five nose-to-tail turns.

[9] The Yak-1's armament would be considered too light by Western standards but was typical of Soviet aircraft, pilots preferring a few guns grouped on the centerline to improve accuracy and reduce weight.

The US and Britain considered heavy armament and high performance necessary, even at the cost of inferior maneuverability, while the Soviets relied on the marksmanship of their pilots coupled with agile aircraft.

Even with the Yak-1's light armament, to reduce weight, modifications were made on the front line and on about thirty production aircraft: the 7.62 mm ShKAS machine-guns were removed, retaining only the single ShVAK cannon.

Nevertheless, these lighter aircraft were popular with experienced pilots, for whom the reduction in armament was acceptable and combat experience in November 1942 showed a much improved kill-to-loss ratio.

[15] Twenty-four of these aircraft were sent to the all-female 586th Fighter Aviation Regiment, whose pilots included the world's only female aces: Katya Budanova, with 5, and Lydia Litvyak (claims range between 5 and 12, plus two shared).

[4][5] That total would also make the Yak one of the most prolific aircraft in history, roughly equal to the best known Soviet ground attack type of World War II, the IL-2 Shturmovik.