An airplane flies at the same speed relative to the air at a high altitude from New

Question:

An airplane flies at the same speed relative to the air at a high altitude from New York to Paris and back.
a. The New York to Paris flight takes less time.
b. The Paris to New York flight takes less time.
c. The two flights take the same time on the average.
d. Any of these can be true, depending on the season.