You're departing tomorrow, wishing you a pleasant journey!
Tips
usage
一路顺风 emphasizes a smooth, pleasant journey, while 一路平安 emphasizes safety. Both are common farewell wishes for travelers.
culture
Traditionally, some people avoid saying 一路顺风 to someone boarding a plane, since 顺风 (following wind) might imply the plane needs wind to fly. 一路平安 is considered safer for air travel.