Robin Edwards, a student on our MRes in Advanced Spatial Analysis and Visualisation here at the Centre for Advanced Spatial Analysis, University College London, has used Processing to create a visualisation using data from OpenFlights.org. The clip below visualises approx 50,000 active flight-paths,interpolating motion along great circle paths for dynamic effect:
Robin notes that it does not account for multiple airlines or scheduled flights, but the path data still seems a reasonable proxy for flight visualisation.