The "sound of freedom" has long referred to the distinctive acoustic signature of a combat aircraft making a high-speed, low-altitude pass. In the free world, pilots use such demonstrations to entertain. In Afghanistan and Iraq, pilots use identical demonstrations - termed "show of force" or "air presence" missions - to deliver precisely targeted effects on the battlefield. Air presence, along with the lesser-included case of tactical shows of force, is an operationally effective, doctrinally legitimate way to employ airpower against an insurgency. A tactical show of force is the use of aircraft under terminal control to threaten or warn a known force possessing hostile or ambiguous intentions. Air presence is the use of aircraft to produce calculated psychological effects directly on a target population by being visible or audible. Driven by Airmen's desire to continually offer better support to the ground forces, air presence emerged in Central Command Air Forces (CENTAF) during Operations ENDURING FREEDOM and IRAQI FREEDOM.