(CNN) - Air passengers in the US have been removing their Covid-19 face coverings after a federal judge ruled that the government's mask mandate on commercial planes was unlawful.
Los Angeles, CA - April 18: A federal judge in Florida has voided the national mask mandate covering airplanes and other public transportation as exceeding the authority of U.S. health officials in the coronavirus pandemic. However, the majority of travelers at Los Angeles International Airport were still wearing their face coverings, in Los Angeles on Monday, April 18, 2022. (Photo by Brittany Murray/MediaNews Group/Long Beach Press-Telegram via Getty Images)
The Centers for Disease Control and Prevention had previously insisted mask rules remain in place until May 3, but the judge in Florida struck down that directive on Monday.
Airlines have already begun relaxing mask requirements but not without some initial confusion.
So what are the new rules? Do they apply to international travel? How safe is flying maskless? Here are the answers to some of the key questions.
What are the new rules for flying with masks in the US?
Most major airlines in the United States have made mask wearing optional following the latest legal ruling, although some have said that face coverings may be required when flying to or arriving at certain destinations.
In the wake of the new ruling, the government's Transportation Security Administration (TSA) says it will not enforce mask wearing on public transport or hubs.
Airlines have enforced their own mask rules in the past, before the mandate was enforced, but most have now rescinded the requirement.
Which airlines have made masks optional?
Major US airlines announced on Monday that masks are now optional on their aircraft.
Delta Air Lines, American Airlines, United Airlines, Southwest Airlines, Alaska Airlines, JetBlue, Spirit Airlines, Frontier Airlines, Allegiant Air, Hawaiian Airlines and Sun Country Airlines have all ceased to require face coverings.
This means both passengers and crew members for these carriers are no longer required to wear them on domestic flights at present.
Will the rules change again?
Uncertain. The removal of the mandate was abrupt development after US District Judge Kathryn Kimball Mizelle overturned the mandate.
A Biden administration official later confirmed that the order would not be in effect while the ruling is under review. It's not immediately known how long that review will be and what will result from it.
"The agencies are reviewing the decision and assessing potential next steps," the Biden administration official said Monday night. "In the meantime, today's court decision means CDC's public transportation masking order is not in effect at this time."
Mask requirements for US travelers were initially enforced by major airlines in the spring of 2020, before being federally mandated in February 2021 for airplanes and other public transport methods.
Can I still wear a mask if I want to?
Yes. Passengers can still wear a mask on board aircraft if they would prefer to do so. However, mask wearing is not required under federal law while the ruling is being reviewed.
I'm medically vulnerable, what should I do?
According to CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health, a "high-quality mask" such as a N95, KN95 or KF94 remains a hugely important tool when it comes to reducing the risk of infection, particularly while in indoor, public spaces.
"My recommendation is that immunocompromised people should mask when indoors around those of unknown vaccination status," Wen told CNN Health last month.
"Others should decide based on how much they want to avoid contracting Covid-19 and the importance of being unmasked."
Do I still need to wear a mask for international flights?
This is likely to depend on the airline, and/or the destination you are traveling to.
United Airlines released a statement on Monday declaring that masks would not be required on "select international flights," while American Airlines has noted that masks may be necessary "from certain international locations based on country requirements."
Even if not required on board, they may still be required when disembarking at international destinations. It's advisable to check with airlines before flying.
What's the medical advice on mask wearing?
Public health experts recommend that people wear masks that offer the most effective level of protection, especially N95s.
According to Erin Bromage, an associate professor of biology at the University of Massachusetts Dartmouth, unlike face coverings, N95s are able to filter large droplets, as well as the smaller aerosols or particles potentially laden with airborne virus if infected people are around.
N95 respirators approved by NIOSH can filter up to 95% of particles in the air if they are properly fitted.
While KN95s and KF94s are also considered to provide a high level of protection, the main difference is that the US tests, certifies and regulates the N95s public health experts.
Although manufacturers in China test KN95s, they do not meet US regulatory standards and the country's government doesn't have a regulatory body validating them, according to Aaron Collins, a professor emeritus at Mercer University's School of Engineering and a mechanical engineer with a background in aerosol science. Meanwhile, KF94s are regulated by the Korean Ministry of Food and Drug Safety.
"If they're made to the standard and certified by the appropriate boards in their country like NIOSH here, they all do basically the same thing," says Bromage.
What's the risk of catching Covid while flying?
The International Air Transport Association (IATA) has previously stated that the risk of contracting Covid-19 on board a flight is very low, even when factoring in the Omicron variant, which "appears to be more transmissible than other variants in all environments."
However, it's worth noting that enforced mask-wearing was considered to be one of the contributing factors to this, along with the quality of air on board modern jet aircraft, which is regularly refreshed, and the fact that passengers are all facing the same direction on an aircraft.
Last month, Linsey Marr, an expert in transmission of infectious disease via aerosols, told CNN via email that dropping the mask mandate would make sense "as long as cases remain low."
"There is a smaller chance that someone who is infected will be on the plane. And we know that planes have excellent ventilation and filtration, which help reduce the risk of transmission on a plane," said Marr, who is a professor at Virginia Tech.
CNN's Dr. Sanjay Gupta says that because of the rapid air exchange most airplanes are safe environments, but the real risk of air travel is when passing through the terminals and other enclosed spaces.
CNN has approached IATA to determine whether it still considers the risk as "very low" if those on board are not wearing face masks.
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