Everyone can check this, sitting in front of your computer: just check the travel institutions, i.e. Expedia:
When you buy a flying ticket for a long-distance East - West, West - East fly (i.e. Chicago - Warsaw, comparing Warsaw - Chicago), there is always a difference in traveling time, in this case about one hour. Does it prove non - rotating Flat - Earth concept??? Or it's just unrelevant?
P.S.
Of course, it happens also with short distances, only it's more visible with longer ones.
Also, IMO it does not prove if The Earth is flat or globe, but instead it proves if it revolves or not. However, as far as the concept of not-moving-earth is an integral part of the flat-earth concept: when it denies the integral part, it denies entire concept.