"一次飞行的距离" can be translated into English as "the distance of a single flight" or more naturally as "the flight distance for one trip" (though the former is more concise and commonly used in technical or aviation contexts).
If emphasizing the direct measurement of a single flight segment, "the range of a single flight" could also be appropriate in some cases (though "range" often implies the maximum possible distance under certain conditions).
For most general purposes, "the distance of a single flight" is clear and accurate.