A UTM is needed to support the safe, secure and efficient integration of both manned and unmanned aircraft in low-altitude airspace. The emerging challenge is to support aerial operations involving aircraft with widely varying performance characteristics and mission objectives.
Some aircraft will be smaller drones in the sUAS category and include multi-rotors, fixed wing, rotary wing, lighter-than-air and hybrid platforms under 55 pounds. These will be remotely piloted and flown both within and beyond the line of sight of the pilot and operator, and may be manually operated or flown autonomously depending on the mission.
Newer types of unmanned or optionally-piloted aircraft will include the much larger urban air mobility (UAM) vehicle designed to carry passengers and serve as an air taxi, and the unmanned cargo aircraft (UCA) that will ferry bulk-load cargo to distribution centers. Both types favor electric propulsion and are increasingly autonomous. The UAM is typically an eVTOL aircraft and the UCA tends to be a fixed wing design.
Finally, manned aircraft will need priority access to low-altitude airspace for emergency response, law enforcement, fire and rescue and other public safety missions. This will commonly include the use of conventional helicopters as well as more traditional airplanes. Other general aviation will also contend for this airspace for a variety of commercial and public service operations.
Put them all together and you have one big challenge to coordinate their activities, especially in more operationally dense urban areas.