Task: Sentence Ordering
Input (English): Steps: (1) An airline reservation is made (2) The passenger arrives early at the airport (3) The luggage is checked (4) The passenger waits in line (5) The passenger shows their identification and gets a boarding pass (6) The passenger goes to their gate (7) The passenger gets in line when it's time to board (8) The plane arrives at the destination (9) The passenger gets off the plane at their destination.  
Where does the following step fit into the given list of steps: The person boards the plane 
Output (English):  After step 7.