[OpenFlights](http://openflights.org/) is a site for “flight logging, mapping, stats and sharing”.
We’re very pleased to hear they’ve [just released their data](http://openflights.org/blog/2009/10/13/comprehensive-airline-route-data-released/) under the [Open Database License (ODbL)](http://www.opendatacommons.org/licenses/odbl/):
> One of OpenFlights‘ most popular features is our dynamic airport and airline route mapping, and today, we’re proud to release the underlying data in an easy-to-use form, up to date for October 2009. Behold 56749 routes between 3310 airports on 669 airlines spanning the globe.
> The data can be downloaded from our Data page and is free to use under the Open Database License.
See also the OpenFlights package on CKAN: