expression
bon voyage!; have a nice trip!
A warm, standard send-off phrase used when someone is departing on a journey. Slightly more formal than いってらっしゃい, but still natural in everyday speech.
「明日からヨーロッパに行くんだ。」「そうか、良い旅を！」
"I'm going to Europe tomorrow." "Oh, really? Bon voyage!"
空港で友達に「良い旅を」と言って見送った。
I saw my friend off at the airport, saying "Have a nice trip!"
Casual, everyday send-off for someone leaving home or the office, implying they will return. 良い旅を is more specifically for a longer journey or trip.
More formal and old-fashioned; literally 'have a safe journey'. 良い旅を is warmer and more common in modern conversation.
A set phrase composed of 良い (good) + 旅 (journey) + を (object marker), literally 'have a good journey'. The phrase is a modern, natural expression without a complex historical derivation.