  The number of Unmanned Aerial Vehicles (UAVs) continues to explode. Within
the total spectrum of Unmanned Aircraft System (UAS) operations, Urban Air
Mobility (UAM) is also on the way. Dense air traffic is getting ever closer to
us. Current research either focuses on traffic network design and route design
for safety purpose or swarm control in open airspace to contain large volume of
UAVs. In order to achieve a tradeoff between safety and volumes of UAVs, a sky
highway with its basic operation for Vertical Take-Off and Landing (VTOL) UAV
is proposed, where traffic network, route and swarm control design are all
considered. In the sky highway, each UAV will have its route, and an airway
like a highway road can allow many UAVs to perform free flight. The geometrical
structure of the proposed sky highway with corresponding flight modes to
support dense traffic is studied one by one. The effectiveness of the proposed
sky highway is shown by the given demonstration.
