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Today, Unmanned Aircraft Systems (UAS) perform a wide variety of roles and missions from providing surveillance along our borders to engaging and destroying enemy targets on foreign soil. All of these UAS missions are typically restricted in their operating environment, whether it is by a Temporary Flight Restriction imposed on civil airspace or by a specific altitude block for UAS in a military Areas of Operation (AOR). However, as UAS roles, missions and applications expand the need for increasing access to the National Airspace System (NAS) is not only desired but also required.
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Neale et al. (2007) studied this question.