Global airlines are governed by strict 'freedoms of the air' dating back 80 years. They've created some funky routes.

• Global airlines are governed by nine "freedoms of the air," drafted 80 years ago in 1944.
• These dictate how airlines can operate in foreign nations, with some more complicated than others.
• The fifth freedom can give airlines a competitive edge and help capitalize on demand.

Over the past 100 years of shuttling people around the globe in metal flying machines, the world's aviation network has grown into a vast web of intersecting routes that connect nearly every corner of the globe.

Because of the complexities of crossing international borders, commercial carriers follow what is known as the "freedoms of the air" — or the right for an airline to operate within a nation other than its own.

These building blocks of aviation make international connectivity possible. 

According to the International Civil Aviation Organization, or ICAO, there are five official freedoms and four other "so-called" rights, that have been outlined in agreements between countries. ICAO is an agency of the United Nations that sets standards for the global aviation industry.

Drafted in 1944 during what is known as the Chicago Convention, the laws were written as world governments relaxed their grip on airline networks and pricing. This liberalization, however, meant countries with bigger airlines would likely dominate the skies — prompting ICAO to implement strict route regulations.

The governing freedoms not only promote more competition and choice but also allow airlines to optimize routes and increase efficiency, according to FlightRadar24. 

Most international carriers except for a very small few follow the basic freedoms of allowing airlines of one state to fly over or land in another, and vice versa.

Open Skies agreements simplify these international routes, like the one between the European Union and the US that allows any airline registered in either market to fly between the two.

Some freedoms are more complicated, but provide interesting and diverse route options to travelers.

The fifth and eighth freedoms of the air

Beyond the first four freedoms, there is one more officially recognized right, as well as the four "so-called" rights. The latter four were not officially drafted during the 1944 Chicago Convention but are regularly accepted and practiced worldwide.

According to ICAO, the fifth freedom gives an airline of one nation the right to fly between two other countries, so long as the one-stop routes start or end in its home country and all parties agree.

Among the most well-known fifth freedom routes are Emirates' flights from New York-JFK to Milan and Newark to Athens, both flying onward to the carrier's base in Dubai.

Similarly, Singapore Airlines flies between New York and Singapore via a stop in Frankfurt, and Australian flag carrier Qantas flies between Sydney and New York via Auckland, New Zealand, according to Google Flights.

United Airlines' delayed fifth freedom route will fly between the US mainland and Cebu, Philippines, via Tokyo starting in October, the carrier told Business Insider on Monday. It was supposed to start in July — before the FAA launched an investigation after a string of safety incidents at United.

These unique routes can be efficient for airlines trying to serve destinations that a plane can't reach nonstop, like Emirates' fifth freedom between Mexico City and Dubai via Barcelona or Latam Airlines' route between Sydney and Santiago, Chile, via Auckland. 

Still, carriers will make stops on otherwise attainable direct flights because they can capitalize on the high-demand market on both legs — filling more seats and making more money.

Customers may also view carriers like Emirates and Singapore as a more luxe offering than the competing US and EU carriers across the Atlantic.

On the other hand, an airline that wants to serve a low-demand market can better fill the plane by adding a fifth-freedom leg to a nearby city, like Dutch flag carrier KLM's flight between Amsterdam and Santiago via Buenos Aires. 

Among ICAO's most interesting "so-called" rights is the eighth freedom, which gives an airline the right to fly between two cities in a country that isn't its own— but the domestic leg seats cannot be sold as the entire journey must start or end in the foreign airline's home nation.

Qantas used to fly an eighth freedom route between New York and Sydney via Los Angeles — but only those originating or destined for Australia could fly on the domestic cross-country leg, Forbes reported.

Also no longer flying, per Cirium data, African carrier Air Senegal, for example, launched a flight from Dakar to Baltimore with a layover in New York in 2021. The domestic leg seats couldn't be sold.

Here's a closer look at the freedoms of the air.

"Five Freedom Agreements"

First Freedom

This allows an airline of one nation to fly over another without landing.

Second Freedom

This allows an airline of one nation the right to land in another territory for a technical stop. Think refueling or an inflight mechanical issue that prompted an unplanned emergency landing.

Third Freedom

This allows an airline of one nation to carry passengers to a foreign state, and vice versa.

Fourth Freedom

This allows the airline of one nation to take on passengers originating in another. The fourth freedom is simply the reverse of the third freedom.

Fifth Freedom

This allows an airline of one nation to carry passengers between two countries other than its own so long as the route starts or ends in the carrier's home state.

"So-called" rights

Six Freedom

This allows an airline to carry passengers from one nation to another via its home state. This represents the typical hub-and-spoke network used by global airlines.

Seventh Freedom

The seventh freedom is similar to the fifth freedom but takes out the limitation of where the route must start or end. Instead, an airline has the right to fly between two nations other than its own without flying onward to its home base.

The EU's single-aviation market, for example, grants airlines the right to fly to and from any EU country, like Ireland-based Ryanair that flies between Rome and Vilnius, Lithuania.

Eighth Freedom

This allows an airline to fly between two cities in a foreign country so long as all passengers originate or are destined for the airline's home state.

Ninth Freedom

This cabotage freedom allows an airline of one nation to fly between two points in a separate single country. This does not exist in the US, but it does in the EU — like easyJet's back-and-forth nonstop between Paris and Nice, for example.