Ace Trip (Targeting, Weapon Mastery)Source Weapon Master's Handbook pg. 20
You can trip flying opponents with your ranged attacks.
Prerequisites: Dex 13, Deadly Aim, Ranged Trip (Ranged Tactics Toolbox 9), base attack bonus +6, weapon training class feature with a ranged weapon.
Benefit: You don’t take the –2 penalty for making trip attempts with a ranged weapon using Ranged Trip, and you can attempt special ranged trip combat maneuver checks against flying creatures. If the combat maneuver succeeds, the target falls at a rate of up to 100 feet per round (assuming it is conscious and attempting to remain airborne; otherwise, it falls at a rate of 500 feet per round) until it hits the ground. Upon impact, it falls prone and takes falling damage (half the normal damage if it fell 100 feet per round; otherwise, normal damage for the distance fallen). A falling creature is considered entangled until it hits the ground, but it can attempt a Fly check at the start of its turn to stop falling before it hits the ground (DC = 15 + your base attack bonus); otherwise, it is unable to move (other than falling) but can act normally.