Boarding
Embarkation
noun, verbal noun
When you board a plane or a car to take a ride it's called boarding or embarkation. You have to get on the right way or you can't ride.
This is a jukugo word that uses the on'yomi readings of the kanji. You should know those readings for both of these kanji by now, so you should be good to go.
ご搭乗の際は、足元にお気をつけください。
Please watch your feet while boarding.
乗客を全員搭乗させると、係員はドアを閉めた。
Once all the passengers had boarded, the attendant closed the door.
えっ、搭乗手続きもしてないのに、どうやって搭乗口に来たんですか？
Huh? How did you get to the boarding gate when you haven't even been through check-in?