I think the two largest challenges faced by the various industries that employ unmanned systems are regulatory and legal, particularly in inconsistencies across Local, State and Federal regulation, and secondly, safe integration into the NAS, which is mostly dependent on NextGen and autonomous technology.
In 2016, the FAA, which has the jurisdiction to exclusively regulate US airspace, released a factsheet advising local and state government what regulations they can enforce with respect to federal regulations and in what ways they may regulate the use of unmanned systems (Kiethley, 2016). This becomes problematic in some cases, like in Cleveland Ohio, where legislation was passed to give local law enforcement the authority to regulate airspace parallel with the FAA’s (Roetzel & Andress, 2016). But any local or state legislation would be technically be null since these levels of government do not have the authority to legally regulate airspace. Additionally, state and local governments may contradict FAA regulations if a court, at some point, and within the context of their locality or state, decide FAA regulations to be inadequate or unsafe. Other cases show state obedience to federal authority in regard to these issues. For example, Governor Jerry Brown of California was presented with several bills in 2016 regarding unmanned systems, of which he vetoed the ones pertaining to matters in which the FAA has jurisdiction (Zimmitti, 2016).
On the other hand, while having inconsistent regulations across the country may stifle industry growth, make FAA control complicated or impossible, or create legal burden, they may also, at times, be advantageous to the public within the context of the locale or state.
The FAA has been slower to open the door to a wider commercial use compared to countries like Japan or Canada due to necessary safety considerations with the more complex US airspace, which leads to another large challenge that I think industry faces:
The second most imposing challenge to the various industries of unmanned systems is safety, particularly the safety of other manned aircraft and those on the ground. Progress to overcome this challenge can be observed in the state and readiness of the air traffic system to control and integrate UAS traffic, and autonomous technology including sense and avoid systems. The FAA has identified sense and avoid as a minimum requirement to integrate UAS into the NAS, and is crucial to the fruition of NextGen Airspace. The FAA takes an approach in which manned aircraft have priority and unmanned systems need to be able to communicate or at least sense the positions of other aircraft, even if those aircraft do not have cooperating technology. The DoD told Congress in 2014 that reliable sense and avoid technology was 2-3 years away (McCaney, 2014). The FAA expressed plans to develop the framework to certify sense and avoid systems by 2016.
References:
Carey, B. (2013). FAA plans unmanned ‘sense and avoid’ rule in 2016. Aviation International News. Web. 16 June 2017. Retrieved from http://www.ainonline.com/aviation-news/air-transport/2013-07-22/faa-plans-unmanned-sense-and-avoid-rule-2016
McCaney, K. (2014). Air force ups the ante on sense-and-avoid UAV technology. Defense Systems. Web. 16 June 2017. Retrieved from https://defensesystems.com/articles/2014/10/21/air-force-sense-and-avoid-uav-contract.aspx
Pillsbury. (2016). FAA clarifies federal, state, and local regulation of UAS. Lexology.com. Web. 16 June 2017. Retrieved from http://www.lexology.com/library/detail.aspx?g=59850149-520e-44bc-b12f-eae0e4e82127
Roetzel, & Andress. (2016). State and local governments considering drone laws should consult with the FAA. Lexology.com. Web. 16 June 2017. Retrieved from http://www.lexology.com/library/detail.aspx?g=af0c3e17-739b-4bda-9ed7-5d101d45cc71
Zimmitti, A. (2016). A look at federal preemption of state drone laws. Law360.com. Web. 16 June 2017. Retrieved from https://www.law360.com/media/articles/854886/a-look-at-federal-preemption-of-state-drone-laws