What is a fifth freedom flight?

A flight operated by an airline between two foreign countries, as part of a route originating in its own — and the resulting services are frequently the most interesting ones in aviation, because they put unexpected aircraft on unexpected routes.

The freedoms of the air are a set of traffic rights negotiated between countries, since an airline has no automatic right to fly to or over another country:

First freedom — to fly over a country without landing.

Second freedom — to land for refuelling or maintenance, without carrying traffic.

Third — to carry traffic from your own country to another.

Fourth — to carry it back.

Third and fourth together are ordinary international service.

Fifth freedom — to carry paying traffic between two other countries, on a route that begins or ends in your own. So an airline flying from its home country to A and onward to B may sell tickets for the A-to-B segment alone.

Why they exist: historically, to allow long routes to be operated economically when aircraft could not fly far enough without stopping. Filling the intermediate segment with local traffic made otherwise marginal routes viable.

Why they persist even with aircraft that could fly direct: they add capacity on routes the local carriers serve, frequently with a better product than would otherwise be available, and they generate revenue on a segment the aircraft was flying anyway.

Why travellers seek them out. A fifth freedom route can put a long-haul aircraft, with lie-flat seats and full service, on a short regional hop that would normally be flown by a narrow-body — occasionally at a competitive fare. Enthusiasts track them for exactly this reason.

The higher freedoms: sixth — carrying traffic between two foreign countries via your own hub, which is the entire business model of the large connecting hubs; seventh — operating entirely outside your own country; eighth and ninth — cabotage, carrying domestic traffic within another country, which is almost universally prohibited.

Rights are negotiated bilaterally or through open skies agreements, and are genuinely political — fifth freedom rights are frequently refused to protect national carriers.