This is the 7563rd most frequent Korean word.
탑승한
"탑승한" means "boarded" or "embarked."
탑승한 in this sentence is used as an adjective describing the passengers who are aboard the airplane.
그 비행기에 탑승한 승객은 모두 안전하게 착륙했다.
The passengers aboard the airplane all landed safely.
Here, 탑승한 is used as a part of the verbal phrase, indicating the instance of boarding before performing the next action.
탑승한 후 좌석에 앉아 안전벨트를 착용하세요.
After boarding, sit on your seat and fasten your seatbelt.
탑승한 functions adjectivally, specifying the passengers who are currently aboard the train for contextual clarity.