[1] In 1935, now with the rank of squadron leader, Swain became a test pilot in the experimental section at the Royal Aircraft Establishment (RAE) where he was involved in high-altitude experiments.

Departing from Farnborough, Hampshire at 07:30 on 28 September 1936, Swain achieved a fixed-wing aircraft's world altitude record with a height of 49,967 ft in a modified Bristol Type 138A.

[4] During his descent, his pressure suit failed causing him to lose visibility through his visor and find it difficult to breathe.

He was forced to cut his visor open with his knife in order to maintain consciousness, eventually landing safely at Netheravon, Wiltshire at 10:30.

Swain married American Sarah Mitchell Le Fevre in Portsmouth on 5 November 1938, going on to have three children together.