(CNN) — The world's busiest airports list is out for 2019, highlighting just how precipitously air travel has plunged amid the coronavirus pandemic.
The preliminary data, released Tuesday by airport trade association Airports Council International, shows that passenger traffic at the world's top 20 busiest airports grew by 1.7% in 2019.
But that was before the Covid-19 crisis brought airports around the world to a near standstill.
"The demand is pretty much gone," said Angela Gittens, ACI World's director general. Traffic is down by more than 90%, she said, and border restrictions and long quarantines for travelers are in effect in many places.
ACI estimates that 4.6 billion fewer passengers will pass through airports in 2020, with a $97 billion reduction in revenue.
Passengers wait to board a flight at Hartsfield-Jackson Atlanta International Airport on April 20, 2020.
Rob Carr/Getty Images
The world's busiest airport, Hartsfield-Jackson Atlanta International Airport saw 110.5 million passengers in 2019.
In the first quarter of 2020, the Atlanta airport logged 20.7 million passengers, down more than 18% from the same period last year.
The steepest declines in passenger traffic in the first quarter of 2020 appeared in China, where the novel coronavirus emerged. Beijing Capital International Airport saw a 62.6% decline in passengers in the first three months of 2020.
Beijing Capital International Airport was the world's second busiest airport for passenger traffic in 2019, with 100 million passengers. Los Angeles International Airport was the third busiest with more than 88 million passengers last year and a 21.7% drop in traffic due to coronavirus.
Chicago O'Hare remained the busiest airport in the world in 2019 for takeoffs and landings, with Hartsfield-Jackson Atlanta Airport coming in second.
In 2019, Hartsfield-Jackson Atlanta International Airport saw 110.5 million passengers.
The challenges for airports
Many of an airport's costs -- such as maintenance and security -- are fixed, even when there's no revenue. "You can't park your runway. You still have to maintain it," Gittens said.
"The challenge, really, is to survive," she said of what the world's airports are facing.
That's why airports are actively seeking relief from governments in the form of waived taxes, concession fees and capital investment requirements. Governments need the connection their aviation systems provide to recover economically, Gittens said.
"We're still in the tunnel ... We haven't seen any light yet. We don't know how long this is going to last at this level," she said.
And in cases where reopenings are not coordinated and rational, Gittens fears a resurgence of the disease or that people will be too afraid to travel because of the perceived risk.
A nearly empty terminal is pictured at Beijing Capital International Airport on April 13, 2020. In 2019, it was the world's second busiest airport.
NICOLAS ASFOURI/AFP/AFP via Getty Images
Getting air traffic moving again
Safety -- for passengers and airport staff -- is paramount and that's what airports say they're are working on with airlines and governments.
Those measures involve personal protective equipment for staff and mask requirements for passengers, as well as physical changes to airports to accommodate social distancing.
With passenger volume so low right now, maintaining social distancing is feasible, Gittens said. "But that's not going to be sustainable. It doesn't take many flights at one time before you can no longer practice social distance."
So masks and thorough hygiene measures for high-touch surfaces will be key. ACI has compiled a set of operational practices adopted by global airports to help guide airports' response to coronavirus.
Resuming air travel safely is not going to a one-size-fits-all proposition, Gittens said. How operations resume should be tailored to the prevalence of the virus in the area.
Los Angeles International Airport on April 16, 2020. In 2019, LAX was the third busiest airport in the world.
Valerie Macon/AFP/Getty Images
Managing the 'passenger hassle factor'
If the virus is somewhat contained or contained, the mitigation measures will be different than if the virus is still spreading widely.
"There's a certain passenger hassle factor which is going to have to be in place for protection, but we don't want to keep the hassle when it's no longer needed," Gittens said.
"The line will be out the door if you keep social distancing once you start having a few more flights. Passengers will have to come to the airport four hours in advance because of the line ... but we don't want to keep that any longer than is needed," she said.
So airports will be in constant consultation with health officials, and when testing becomes more prevalent, test results may help ease some of the other mitigation measures, Gittens said.
In 2019, LAX saw 88 million passengers.
Mark Ralston/AFP/Getty Images
ACI has been working with governments in trying to achieve a more touchless traveler experience -- with more facial recognition and iris recognition and fewer touchscreens and shared documents.
But in the meantime, all of those high-touch areas need thorough and frequent cleaning.
Even before the pandemic, ACI was working on a project called Smart Security, which focuses on having fewer checkpoints in airports and smoother, more digital ways of checking people.
Because anywhere that passengers have to stop means lines and crowds, Gittens said.
And right now, that also means increased traveler anxiety.
Here are 2019's busiest airports by passenger volume and how much their traffic dipped at the start of 2020:
World's 10 busiest airports by passenger volume in 2019
1. Hartsfield-Jackson Atlanta International (ATL) -- 110.5 million passengers
2. Beijing Capital International (PEK) -- 100 million
3. Los Angeles International (LAX) -- 88.1 million
4. Dubai International (DXB) -- 86.4 million
5. Tokyo International (Haneda) (HND) -- 85.5 million
6. Chicago O'Hare International (ORD) -- 84.6 million
7. London Heathrow (LHR) -- 80.9 million
8. Shanghai Pudong International (PVG) -- 76.2 million
9. Paris-Charles de Gaulle (CDG) -- 76.2 million
10. Dallas/Fort Worth International (DFW) -- 75.1 million
Pandemic impact: Q1 2020 traffic declines from Q1 2019
1. Hartsfield-Jackson Atlanta International (ATL) -18.2%
2. Beijing Capital International (PEK) -62.6%
3. Los Angeles International (LAX) -21.7%
4. Dubai International (DXB) -19.9%
5. Tokyo International (Haneda) (HND) -28.5%
6. Chicago O'Hare International (ORD) -- n.a.
7. London Heathrow (LHR) -18.3%
8. Shanghai Pudong International (PVG) -57.1%
9. Paris-Charles de Gaulle (CDG) -20.6%
10. Dallas/Fort Worth International (DFW) -12.3%