Hélène Dutrieu, 1877–1961, first became famous as a speed cycling world champion in 1897 and 1898 (yes, in the 19th century and wearing trousers) which earned her the nickname "The Human Arrow". She went on to become a stunt cyclist, stunt motorcyclist, automobile racer, stunt driver, pioneer aviator known as the "Girl Hawk", wartime ambulance driver, director of a military hospital, and a journalist.
Early in her aviation career Dutrieu was the subject of a minor scandal when the press revealed that she didn't wear a corset while flying!
The New York Times observed the clothing of lady pilots in 1911: "The accepted toggery is a two piece suit consisting of a blouse and knickerbockers or trouserettes. The headgear differs according to the feminine idea. It may be an automobile cap or a becoming hood of some soft material."
The U.S. press were, however, loudly disappointed at the flying gear worn by the famous European aviatrixes who visited America. They compared the European preference for practical brown serge, dark leathers and muted woollens unfavourably with the brightly-coloured and shiny satins worn by several well-known American aviatrixes. Nevertheless the following photo is one of the best early aviation fashion shots I've seen (almost certainly featuring brown serge). It's Hélène Dutrieu, circa 1908-9, next to a tiny ultralight monoplane which is probably a Santos-Dumont designed no.19 or no.20 also known as the Demoiselle or "Young Lady".