My daughter and I had to go to the airport to get on a airplane to go on a trip.  We got there early in the morning so we could have a lot of time.  We  checked to see if we could still get on the plane on time.  We checked to see if we had our passports which we had to have if we wanted to go on a plane.  We had to make sure we were at the right place because we didn't want to get lost.  We had to find our airplane.  You can get lost on them like you can a bus.  We found it.  We still had fifty minutes so we went in the airport restaurant to get a cup of coffee and a donut.  The donut was delicious.  It had jelly in the middle.  We checked our bags to make sure we had everything then we got on the plane.
Why did they bring their passport?