We used to travel with the Prophet ﷺ, and whenever we ascended we would say "Allahu Akbar," and whenever we descended we would say "Subhan Allah."
حدثنا روح حدثنا أشعث عن الحسن
كنا نسافر مع النبي ﷺ فإذا صعدنا كبرنا وإذا هبطنا سبحنا
Its isnad is sahih. See 13438.