The number of air travelers is soaring in the U.S. — and flying in the face of federal health guidance. The Transportation Security Administration has reported five consecutive days of more than 1 million air travelers, including the single highest day for passengers since March 2020.

The data show that the popularity of plane travel is taking off again a year into the pandemic, despite Centers for Disease Control warnings that it could contribute to another COVID-19 surge.

TSA numbers show there were more than 1 million U.S. plane travelers each day between March 11 and March 15. On March 12, there were 1,357,111 travelers — the most on any day since March 15, 2020, just four days after the World Health Organization declared COVID-19 a pandemic.

Travelers stayed grounded for most of 2020, with the TSA recording less than a million air passengers passing through checkpoints nearly every day after the pandemic began. The low point was April 14, with only 87,500 passengers. The airline industry cut back on flights after experiencing an unprecedented loss of billions of dollars in revenue. 

Plane travel started lifting off again at the end of 2020, and has picked up even more as COVID vaccinations have begun. The TSA has reported 17 days of more than 1 million passengers since late February.

Federal health officials advised against plane travel during the 2020 holiday season, and are continuing to discourage it now, saying that spikes in travel lead to spikes in cases. 

In a White House briefing Monday on the pandemic, CDC Director Rochelle Walensky said the rise in air travel could contribute to a spring surge, along with the warmer weather and people celebrating spring break without masks.

“I’m pleading with you, for the sake of our nation’s health,” Walensky said. “These should be warning signs for all of us. Cases climbed last spring, they climbed again in the summer, they will climb now if we stop taking precautions when we continue to get more and more people vaccinated.”

TSA spokeswoman Lisa Farbstein has tweeted several times about the jump in numbers, reminding passengers that they must wear masks.