For the past 18 months, the travel downturn has played havoc with airlines and airports worldwide. Some big-name global aviation hubs have seen their status diminished while others have been suddenly thrust into the spotlight. If you are missing the pre-downturn chaotic airport vibe, here's a rundown on some of the busiest airports in the world today.

Recently published OAG data reveals the ten busiest airports worldwide in August as measured by available seats. OAG points out only four of the airports making the list this month were in the top ten in August 2019.

Atlanta Airport is still the worlds busiest airport on seat availability metrics

Heading the list is Atlanta's Hartsfield–Jackson International Airport (ATL), with 4,664,777 seats available on flights in and out of the airport in August. Atlanta was also the world's busiest airport in August 2019 when assessed by seat availability.

Six airlines, including Delta Air Lines, are based in Atlanta. What is interesting about Atlanta is the relatively small number of airlines servicing the airport. According to aviation database ch-aviation.com, only 27 airlines fly in and out of ATL.

But Delta's presence in Atlanta helps boost the airport's connectivity. Atlanta has nonstop flights to 239 destinations in 47 countries.

The second busiest airport worldwide in August 2021 is Dallas Fort Worth (DFW). The airport had 3,839,131 seats available across August. The second placing is a big jump up the ranks for DFW. The airport was the world's 11th busiest in August 2019.

Dallas Fort Worth gets a considerable lift from American Airlines who based themselves there. Like Atlanta, the sheer number of seats American offers boosts DFW in the rankings.

Aside from American, 32 other airlines fly in and out of Dallas Forth Worth. Between them, the airlines fly to 273 destinations in 44 countries. That makes Dallas a better-connected airport than Atlanta.

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Photo: Dallas Fort Worth Airport

US airports top the busiest airport rankings

Also soaring up the rankings is Denver International (DEN), who ranked third busiest in August compared to 17th busiest in August 2019. Denver had 3,746,287 seats available on flights in and out of the airport over August.

Denver isn't the home port of any major airline, but it is a major hub for United Airlines and Frontier Airlines and a base for Southwest Airlines. A fairly tight 23 airlines presently serve the airport flying nonstop to 229 destinations in 14 countries.

Denver's lack of international connectivity is symptomatic of the travel downturn. International arrival and departure points have focused on a handful of airports in most countries. That trend is also clear in the United States.

The fourth spot goes to Chicago O'Hare Airport (ORD), which offered 3,743,754 seats on flights this month in and out of the airport. In August 2019, ORD was ranked sixth. Like ATL and DFW, O'Hare benefits from being the home port of a major carrier, in this case, United Airlines.

Chicago O'Hare's status as a global hub is affirmed by the 58 airlines that still fly into the airport. That's more than double the number of airlines that fly into either Atlanta or Denver. Those 58 airlines fly to 291 destinations in 55 countries.

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Photo: Chicago O'Hare International Airport

LAX rounds out the busiest US airports

Rounding out the US airports is Los Angeles International (LAX). With 3,317,253 seats on offer in August, LAX is the fifth busiest airport in the world. The airport was the same ranking in August 2019.

Los Angeles International has a whooping 13 airlines based there. Unfortunately, none of them are big carriers. However, the airport is a significant jumping-off point for United and American Asia-Pacific-bound flights.

Am impressive 64 airlines fly in and out of LAX. Those airlines fly to 207 destinations in 44 countries.

Having dominated the rankings thus far, US airports now drop off the radar. Miami, JFK, Houston, SFO ... none of them make the top ten list this month when measured by seat availability. In sixth spot this month is Guangzhou's Baiyun International Airport (CAN).

Guangzhou had 3,140,957 seats on offer in August. On the same metric, the airport was the 13th busiest in August 2019. Home to China Southern Airlines, 70 airlines fly in and out of CAN to 224 destinations in 44 countries.

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China Southern's home port of Guangzhou was the sixth busiest airport in August measured by seat availability. Photo: Getty Images

Only one airport outside the US and China makes the top 10

Now, Chinese airports dominate the remainder of the list. The only exception is Istanbul's Ataturk Airport (IST), which offered 2,983,322 seats across August and took the seventh spot in the rankings. In August 2019, the airport was ranked 14th.

Home to juggernaut Turkish Airlines, IST is the most global airport we've touched on so far. Seventy-one airlines fly to and from IST to 312 destinations in 125 countries. Today, there are 474 departures scheduled from IST.

In eighth spot is Beijing's Capital Airport (PEK). Not to be confused with Beijing's new Daxing Airport, PEK had 2,760,172 seats on offer over August. The eighth spot is a significant downgrade for PEK, who took the second spot in August 2019.

Air China is the headline airline based in Beijing Capital. But another 56 airlines jet in and out of the airport. Between them, they fly to 191 destinations in 43 countries.

Beijing, Capital Airport, China Eastern
Beijing's Capital Airport is the home port of Air China. Photo: Getty Images

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Chinese airports round out the top 10 list

Rounding out the top ten busiest airports in terms of seat availability are Shenzhen Bao'an International Airport (SZK) and Shanghai Pudong (PVG). In the ninth spot, Shenzhen had 2,380,766 seats on offer in August. Shenzhen is up from 31st ranking in August 2019.

Home base to 15 airlines, including Shenzhen Airlines and Donghai Airlines, a total of 45 airlines fly nonstop to 168 destinations in 22 countries from Shenzhen.

Shanghai Pudong also ranked 10th in August 2019. The airport may be just making the top ten list, but if we were judging based on different carriers using the airport, PVG would top this list of 10 airports. Eighty-five airlines fly in and out of PVG.

In August, those airlines offered 2,566,526 seats. Between them, these airlines fly to 232 destinations in 45 countries from Shanghai Pudong.

There are many ways to measure the world's busiest airports - the number of flights, passenger numbers, or in this case, seat availability. Different metrics will produce different results. But no matter how busiest airports rankings are evaluated, you'll see significant changes from 2019 results.