The 20 biggest airlines in the world, ranked

• Through recent mergers, airlines such as American, Delta, and United have grown to become colossal mega-carriers.
• Recently, the aviation-data firm OAG provided us with data sets that ranked the 20 largest airlines based on the number of seats each carrier made available to passengers during 2018.
• As expected, US carriers made a strong showing with American, Delta, United, Southwest, and Alaska all in the top 20. 
• The low-cost carriers Ryanair, EasyJet, and IndiGo placed in the top 20.
• Other international carriers to make the list include Emirates, Air China, China Eastern, China Southern, Lufthansa, Turkish, All Nippon Airways (ANA), LATAM, British Airways, Air France, Air Canada, and Aeroflot. 

Over the past century, the airline industry has changed the way humans travel. It has effectively made the world a smaller place — making it possible for billions of people everywhere to explore the world. 

According to the International Air Transport Association (IATA), consumers spent an estimated $871 billion, or roughly 1% of the global GDP, on air travel. 

The trade group, which has a membership made up of 290 airlines, expects the total number of airline passengers around the world to reach 8.2 billion people by 2037 — that's double today's passenger count. 

As a result of the industry's growth, many of the world's airlines have become household names. Through recent mergers, American, Delta, United, and Southwest have grown to become colossal mega-carriers. 

Read more: The 11 longest flights in the world, ranked

This got us at Business Insider thinking about how they stack up against the largest airlines. 

Fortunately, the good folks at OAG provided us the data sets that answered our question. 

The London-based aviation-data-and-intelligence firm ranked the world's airlines based on the total number of seats each carrier made available to customers during 2018. OAG also included the total number of aircraft in each airline fleet.

Some airlines on the list offer substantially more seats while operating fewer aircraft.

According to OAG senior analyst John Grant, this variation is because of the differences in the planes that comprise a carrier's fleet and the seat configurations of each aircraft. As a result, airlines that operate larger aircraft and aircraft with higher seat density will be able to make more seats available to customers.

Here's a closer look at the 20 biggest airlines in the world: 

SEE ALSO: We flew on Honda's new $5.25 million private jet. Here are its coolest features.

FOLLOW US: On Facebook for more car and transportation content!

20. Alaska Airlines

Capacity: 54,574,295 seats. 

Fleet size: 233 aircraft.

19. Aeroflot Russian Airlines

Capacity: 56,260,035 seats.

Fleet size: 253 aircraft. 

18. Air France

Capacity: 58,888,616 seats.

Fleet size: 206 aircraft.