Go n-éirí an bóthar leat / Go dté tú slán(singular)
Go n-éirí an bóthar libh / Go dté sibh slán(plural)
here's a suggestion - Slàn turas is biodh greann mor (with a fada on the 'o') agaibhse.
An answer:
Go n-éirí an turas leat.
Go dté tú slán (singular) Go dté sibh slán (plural)
(To one person): Bíodh an-turas agat (To more than one person): ...agaibh.
Biodh turas maith agat = Enjoy your trip
Bíodh an-turas agat.
In Irish "go dté tú slán"
Bíodh an-turas agat.
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