Travelers arrive at the Detroit Metropolitan Wayne County Airport (DTX) in Romulus, Michigan, on Saturday, June 12, 2021.
CNN  — 

As more Americans get vaccinated against Covid-19 and states and cities further ease pandemic restrictions, more people are flying for vacations, family visits or just getting away.

The Transportation Security Administration screened more than 2 million passengers Friday, the highest number since March 7 of last year, just before lockdowns and coronavirus restrictions started keeping people home.

The data confirms the recent upward air travel trend to levels not seen since before the pandemic: On June 11, 2019, the TSA screened 2.7 million people.

“The growing number of travelers demonstrates this country’s resilience and the high level of confidence in Covid-19 counter measures, to include ready access to vaccines,” acting TSA chief Darby LaJoye said in a statement.

Before the pandemic, the TSA screened on average between 2 and 2.5 million travelers per day.

National parks welcoming hundreds of thousands every month

Another indicator that Americans are getting back out and about: National parks are citing spikes in attendance.

Last month, Yellowstone National Park saw the most visitors it had ever recorded for the month of May, with 658,513 visits – an 11% increase over the previous May record, set in 2016.

It’s also more than four times the number of visitors Yellowstone had in May 2020, when the park was closed for the first half of the month due to Covid-19.

Grand Teton National Park, also in Wyoming, set a May record as well. It had 363,712 visitors last month, 30% above the last pre-pandemic May in 2019. Numbers are likely to go even higher further into the summer.

“Historically, July and August have been the busiest months of the year at the park,” Grand Teton said in a press release Friday.

Delta variant likely to become dominant strain, official says

As travel sets pandemic records, there are warnings that parts of the country could see outbreaks of the B.1.617.2 Covid-19 strain, or Delta variant.

The variant was first detected in India and is about 60% more transmissible than the B.117 or Alpha variant – which was first identified in the UK. The Delta variant makes up about 10% of infections in the United States, according to Dr. Scott Gottlieb, a former commissioner of the US Food and Drug Administration.

“It’s doubling every two weeks, so it’s probably going to become the dominant strain here in the United States,” Gottlieb said in a CBS interview Sunday.

“That doesn’t mean that we’re going to see a sharp uptick in infections, but it does mean that this is going to take over,” he added.

Gottleib said existing Covid-19 vaccines appear to provide some protection against the variant.

“I think in parts of the country where you have less vaccination – particularly in parts of the South, where you have some cities where vaccination rates are low – there’s a risk that you could see outbreaks with this new variant,” Gottlieb said.

More than 309 million Covid-19 vaccine dose