Breeders of homing pigeons have been prevented from letting their birds fly freely.

NPR: China's Bird Flu Response Shows New Openness

The template is that any American airline is allowed to fly freely to and from a country, with no regulation of fares, routes or frequencies.

ECONOMIST: Airlines

Carriers can operate freely from international waters, while land-based aircraft cannot easily fly in a war zone unless a nearby country offers a base.

ECONOMIST: The future of the Royal Navy