A woman was shocked to board a packed American Airlines flight and find that half the passengers were not wearing masks.

Many flights are mostly empty because of the coronavirus pandemic, but the flight from Miami to New York was 80 to 90% full, the New York Post reported.

The news came as the head of the largest flight-attendant union called on the US Department of Transportation to require airline passengers to wear face coverings.

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Airlines around the world are flying mostly empty planes as they maintain connectivity while travel demand plummets because of the coronavirus outbreak.

That meant it was an unpleasant surprise for a New York woman who walked onto a flight from Miami to find that it was packed full — and despite federal guidance for social distancing and face coverings, half the passengers weren't wearing masks.

According to the New York Post, Wednesday's American Airlines Flight 2669 from Miami to New York's LaGuardia Airport was about 80 to 90% full.

When Angie Wong, a New Yorker, boarded the plane wearing a surgical mask, face shield, gloves, and a hoodie, she expected to see a mostly empty flight with passengers covering their faces.

Instead, people wore a wide variety of outfits and protective gear, from standard clothing with uncovered faces to hazmat coveralls.

It was especially surprising, Wong told the Post, because social-distancing rules were strictly enforced in Miami before the 10:19 a.m. flight.

"I could tell passengers were very nervous that masks were not mandated," she told the Post. "I asked how this was allowed during distancing requirements, and got 'nothing we can do about it' shrugs and offered an 800 number to change my reservation."

The news came as America's biggest flight attendants' union demanded that the US Department of Transportation require passengers on commercial flights to wear masks.

Surgical masks and face coverings do not necessarily protect the wearer but have been shown to protect others nearby if the wearer is an asymptomatic carrier of the virus.

Sara Nelson, the president of the Association of Flight Attendants-CWA — which represents flight attendants from 20 airlines but not American — wrote in a letter to DOT Secretary Elaine Chao that masks should be required to be worn on planes and in airports "so long as COVID-19 remains a threat to public health."

"Passengers on all modes of public transport should be encouraged to wear masks in the short term and mandated by emergency regulation as soon as practicable," Nelson wrote. "This will further minimize risks to themselves, the public transport workforce on which they are reliant, and our healthcare infrastructure, which must cope with the surge of infected patients unless we curb the spread."

Seven US states including New York require people to wear masks in public when maintaining social distance is not possible.

Canada recently required all airline passengers to wear masks during travel.

Nelson also called for leisure travel to be banned until the virus is contained.

"Airlines are continuing to deliver people, mail, and cargo, uniting families that are grieving or rushing to be

with those who have fallen ill, and transporting others who require medical treatment unrelated to

the pandemic," she wrote.

"We believe that protecting this essential service and ensuring air travel is not aiding in spread of the virus

requires a halt to all leisure travel until the pandemic is brought under control according to health

authorities," she added.