We rode Flight of Passage twice last February when we visited Animal Kingdom. We were there for rope drop and had a FastPass+ for later in the day.
Arrive at park: 7:30 am for 9 am park opening (aka rope drop)
Wait: at the far left
After they start letting guests in: head to the left
They’ll stop you at the bridge into Pandora: move to the right of the crowd to be on your way to Flight of Passage