Does anyone know who was the first pilot to use supplemental oxygen? I’ve searched Google extensively and came up with limited information. One site says it was Georges Legagneux of France when he set the altitude record of 20,080’ on December 28, 1913. This date agrees with other findings which don’t mention the oxygen use. However, a second site, in French, says that Legagneaux accomplished his record setting flight ‘mais sans respirateur’ (but without a respirator). So I’m left not sure about the answer.
Searching books available so far has not turned up any other information to help. Do any Dopers know anything about this subject?