Female MiG pilot?

The filmmakers weren't concerned with whether there actually were female Soviet fighter pilots or not. It was a plot device, pure and simple.

But if looked at from the mentality of its era, the notion of a woman being a jet pilot was obviously meant to suggest that the Russians had no concept of women as "the gentle sex", but looked at them merely as sexless, humorless comrades doing men's work. It was intended as a disparaging joke, much like the depiction of female Russian dock workers at the end of the 1943 film Action in the North Atlantic -- making fun of the Soviets as ideologues intent, among other things, on deglamorizing women.

It's true, especially under Stalin, that the Soviet regime suppressed art, literature or then-popular concepts like "free love" that emphasized sexuality (men's as well as women's), and the fact that women were used in many occupations usually thought of as "men's work" in the West was viewed as evidence of the regime's failures and desperation. The Soviets were also notoriously prudish, and sex education, and even clinical knowledge about sex, were virtually non-existent under the Soviets. So the caricature played by Katharine Hepburn fit right in with popular (and condescending) western beliefs about Russian women, though like all caricatures there was also some truth to the image.

Hepburn's character says as much about the smirking attitudes towards women in the West so widely held in the 1950s, as it does about the supposed equality of women under the rigid, corrupt and inefficient Soviet system. But at the time western audiences, who were the only people who would ever see this film -- if indeed anyone went to see it -- would have regarded Hepburn's falling for Hope, discovering sex and glamor, and giving up her skills to settle down with an idiot, as the natural state of affairs for a woman.

Jeannie Levitt was the first female active-duty combat fighter pilot; during WWII, there were more than 1100 Women Airforce Service Pilots--WASPs--trained to perform jobs that freed up men to fight overseas. These included ferrying new aircraft from factories to bases and ports, testing repaired aircraft, and towing targets for ground and aerial gunnery training. They were, unfortunately not permitted to actually join the Air Force and only recognized as military members retroactively, in the mid-1970s.

My impression was that Hepburn's character had a similar role; not a combat pilot (although there were female Soviet combat pilots during the desperate days of WWII) but perhaps with a propaganda element, like Hanna Reitsch in Germany.