I think this link here can tell you best why we have a Air Force and what their point is. I have a brother-in-law that just retired from the Air Force.Good luck, best wishes
http://www.airforce.com/
The mission of the United States Air Force is to deliver sovereign options for the defense of the United States of America and its global interests to fly and fight in air, space and cyberspace.
To achieve that mission, the Air Force has a vision of Global Vigilance, Reach and Power. That vision orbits around three core competencies: Developing Airmen, Technology-to-Warfighting and Integrating Operations. These core competencies make our six distinctive capabilities possible.
Air and Space Superiority
With it, joint forces can dominate enemy operations in all dimensions land, sea, air and space.
Global Attack
Because of technological advances, the Air Force can attack anywhere, anytime and do so quickly and with greater precision than ever before.
Rapid Global Mobility
Being able to respond quickly and decisively anywhere we're needed is key to maintaining rapid global mobility.
Precision Engagement
The essence lies in the ability to apply selective force against specific targets because the nature and variety of future contingencies demand both precise and reliable use of military power with minimal risk and collateral damage.
Information Superiority
The ability of joint force commanders to keep pace with information and incorporate it into a campaign plan is crucial.
Agile Combat Support
Deployment and sustainment are keys to successful operations and cannot be separated. Agile combat support applies to all forces, from those permanently based to contingency buildups to expeditionary forces.
Core Values
The Air Force bases these core competencies and distinctive capabilities on a shared commitment to three values: Integrity first, Service before self, and Excellence in all we do.