Abstract: Air freeways connecting long-distance city-pairs with heavy traffic flow in the next generation aviation transportation system (NGATS) are characterized by monolayer route with single direction, no crossover, aircraft performance limitation, and high density of operation. In order to study the traffic flow operation on the air freeways, a microscopic aircraft-following model for single-layer route of air freeways was established using the car-following theory, based on the civil aviation operation rules of NGATS. Through analysis of the relationship between air traffic flow and density, the model was then extended to a macroscopic traffic flow model for air freeways. The macroscopic model can be used for air route flow optimization, safety analysis, and capacity evaluation. Simulation results of the microscopic aircraft-following model show that the aircraft-following response of a posterior aircraft intensifies when the separation distance from its anterior aircraft is nearer, the speed of flight in the route is faster, or the respond intensity of the posterior aircraft is weaker. Simulation results of the macroscopic air traffic flow model show that the air traffic flow variation is more remarkable when the aircraft separation distance is smaller or the initial velocity is larger.