A dynamic channel assignment method includes receiving, at a ground control station (GCS), assignment of a first communication channel set from a spectrum authority before takeoff of the unmanned aircraft; receiving, at the GCS, assignment of a second communication channel set when the unmanned aircraft is to move from a first area using the first communication channel set to a second area using the second communication channel set due to a flight plan of the unmanned aircraft after takeoff of the unmanned aircraft; and after the unmanned aircraft enters the second area, maintaining, at the GCS, the first communication channel set when the unmanned aircraft reenters the first area due to the flight plan, and returning, at the GCS, the first communication channel set to the spectrum authority when the unmanned aircraft does not reenter the first area due to the flight plan.