Rule 4, Section 2, Article 4"

"d. The most forward point of the ball when declared out of bounds between
the goal lines is the point of forward progress. (A.R. 8-2-1-I and A.R. 8-5-
1-VII) (**Exception: When a ball carrier is airborne as they cross the sideline
(including a striding runner), forward progress is determined by the
position of the ball as it crosses the sideline** (A.R. 8-2-1-II-III and V-IX)."