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flight (e.g. airline flight); trip (e.g. train trip); service
mail; post; letter
opportunity; chance
「便」 has another reading with different meanings.
朝一番の便に乗るために早起きしなければならない。
I have to wake up early to catch the first flight of the morning.
次の便で送っておきますね確認してください。
I'll send it on the next mail.
朝一番の便に乗りたいんだけど。
I want to take the first morning flight.