Thanks for the replies, and good point about the decompression, Ranko.
I was looking at the altitude and speed records for aircraft at the time. I'm not sure if the altitude is the same in the original 1938-39 Coeurs Vaillant version of the story, but the Stratoship would have been setting - or pretty much equaling - the altitude record for the time. In 1936 the record was set by the Bristol Type 138 at 49,967 ft (15,230 metres). The pilot, Squadron-Leader Francis Ronald Swain, wore a pressure suit that looked very much like a 1930s version of a spacesuit
. During the record-breaking flight the suit and cockpit began to frost over, so he descended but felt it difficult to breathe so broke the glass of his helmet fearing this the cause.
See this Pathé news clip about the flight
featuring an interview with Squadron-Leader Swain!
Does anyone agree it's possible that Hergé was aware of this flight and - with his keenness for accuracy and research - not too much a stretch that it was an influence on that particular episode in Mr Pump's Legacy
Most people have heard of the 'Space Race' of the fifties and sixties, but less known is the 'Air Race' of the twenties and thirties where nations and companies competed for the prestige of breaking flight records. Records were constantly being broken, the altitude record being set twice in 1936, once in 1937, twice in 1938, etc.
The speed record of 1,000km/h reached during the Stratoship test flight wasn't ever
achieved in a propeller aircraft, at least not a piston driven one. Also, Mr Pump's challenge was for someone to fly from New York to Paris (or vice versa) at an average
speed of 1,000km/h, so it would have had to have flown faster. It seems it still holds that particular record.