Strafing Breath( Dragonlance Campaign Setting, p. 87)
You can sustain your breath weapon when you use it on the wing, covering a larger ground area in its effect.
When you use your breath weapon while flying (either with a single move, using the Flyby Attack feat, or with a double move, using the Flyby Breath feat), you can extend the area covered by your breath weapon on the ground. You can use your breath weapon over a distance up to half your fly speed if you move in a straight line along that distance. To determine the affected area, find the area your breath weapon would normally affect on the ground, then extend that area in a straight line the desired distance. Measure the extended distance from the center of the effect.
For example, an adult blue dragon has a fly speed of 150 feet, and its breath weapon is a 100-foot line of lightning. Normally, its breath weapon would cover a single 5-foot-by-5-foot circle on the ground, since a line is 5 feet wide and 5 feet high. Using Strafing Breath, it can cover an area 5 feet wide and 75 feet long (half its fly speed).
An old red dragon has a fly speed of 200 feet, and its breath weapon is a 120-foot cone. If it is flying at an altitude of 80 feet, its breath weapon affects a circle on the ground with a radius of 80 feet. Using Strafing Breath, it can cover an oblong area 80 feet wide and 180 feet long, with both ends shaping like half circles.