Strike from Below

If you have Extra Attack, you may use this maneuver in place of one attack.

You command your animal companion to leap at a flying creature and target its means of flight. Your animal companion may move up to 20 feet to get into position and gains a vertical jump height equal to half its Speed for the purposes of striking the target creature. The creature is forced to make a Dexterity saving throw . On a failure, its flight speed is reduced by half until healed and it immediately plummets to the ground (or 60 feet, whichever comes first) and takes falling damage as usual. On a success, it takes damage equal to your proficiency bonus. Creatures more than 1 size category larger than your animal companion make this save with advantage .

Regardless of the result, after performing the maneuver, your animal companion lands in an unoccupied square of your choice that is adjacent to the one directly below the target, taking fall damage as normal. If there are no unoccupied adjacent squares, your animal companion falls either into the square directly below the target creature (which may, in turn, fall on your companion) or onto the creature in the adjacent occupied square of your choice. Both the creature that falls into an occupied square and its occupant take double the normal amount of fall damage before the falling creature is shunted into the closest unoccupied space.