Have a nice trip! = Miłej podróży!
Have a nice trip = Bon voyage! (Not sure what you mean by "When you are flight".
¡Buen viaje! (Have a nice trip!)
Buon viaggio.
bon voyage!
Slán agus beannacht leat.
Lá breá a bhí ann.
Golgu todu show du
Tá folt breá ort
Go deas bualadh leat.
In West Galway you could say "Tá áthas orm casadh leat".
Merci avoir un bon jour no, that's French