While conditions begin to improve, many U.S. travelers flying back from Europe were greeted with snaking lines and hours-long waits at major airports as expanded coronavirus screenings required by the government's new European travel restrictions took effect this weekend.

The restrictions ban Europeans from flying to the United States for 30 days and require U.S. travelers to be screened upon arrival at 13 U.S. airports.

Travelers at Chicago O'Hare International Airport, New York JFK and Dallas-Fort Worth International Airport took to social media to complain about the waits, with many worried that the logjam wasn't helping stop the spread of coronavirus.

College student Brandon Mach, who was flying back Saturday from Madrid, said he waited more than four hoursto clear U.S. Customs and Border Protection and go through Centers for Disease Control and Prevention screening at O'Hare. The Michigan resident said he landed at 4 p.m. and didn't leave until nearly 9 p.m., until his temperature was checked and he was asked a few questions.

"What better way to 'avoid large gatherings,' " he tweeted.

Mach, 20, told USA TODAY he had to go through customs twice, a second time after he told officials he was returning from Spain, where his semester abroad was cut short. The country went on lockdown Saturday as the result of a surge in coronavirus cases.

"That was by far one of the craziest things I've seen at an airport,'' he said, noting that the medical screening was actually the quickest part.

Passengers he talked to in line were all going to miss their connecting flights out of O'Hare because of the logjam.

Speaking at a news conference with President Donald Trump and Vice President Mike Pence on Sunday, U.S. Department of Homeland Security Acting Secretary Chad Wolf acknowledged flyers' frustration, but noted that many of the screening airports had improved their process since the initial uproar began. All 13 airports had an average wait time of 30 minutes on Sunday, he added.

"To be clear, the lines that we saw overnight at a limited number of airports including Chicago are unacceptable," Wolf said. He added that U.S. Customs and Border Protection Acting Commissioner Mark Morgan "also believes they are unacceptable and has personally engaged leadership at all 13 funneling airports. We did make the necessary adjustments at 12 of the funneling airports. ... At Chicago, those adjustments were not made quick enough, but we have course-corrected."

At the Atlanta airport, travelers landing from Paris on Sunday afternoon reported a smooth screening process that took about 30 minutes. Travelers said they received a health questionnaire at the beginning of the flight asking which countries they had traveled to and if they had been in contact with someone with coronavirus, among other questions.

When they arrived in Atlanta, airport officials deboarded passengers in sections and did visual checks for coronavirus symptoms as they walked through U.S. Customs, travelers said.

Maddie Turner, who was studying abroad in Paris, said she was relieved to get through customs quickly after hearing about long waits elsewhere.

“I haven’t slept in a couple days,” said Turner, 21, of Atlanta. "I’m looking forward to my heart rate going back down.”

Sandra Mower, who had a flight connection in Paris after taking a cruise to Barcelona, said she was pleased with Atlanta’s screening process.

“I expected to be here several hours,” said Mower, of Demorest, Georgia. “But it was pretty much a breeze.”

Isaiah Hodges, who works for Disneyland Paris, said he rushed to get a flight home to the U.S. after they closed the amusement park. Hodges said he wondered if the screening process in Atlanta was rigorous enough.

“Coming through Paris into Atlanta seemed a little lenient for me,” said Hodges, 24. “Nobody took my temperature or anything.”

Matthew Paragas arrived at LAX on Sunday morning to pick up his aunt, who flew in from the Philippines to visit family and had been waiting more than five hours to be interviewed by customs.

"It's kind of ridiculous, because it's been so long and we're just trying to figure out if we need to wait any longer, if she'll be released," Paragas said. "We just don't know what's going on."

The Bloom family arrived Sunday in Dallas after visiting New York, Paris, Amsterdam and London – "all the hot beds," said Aimee Bloom, 38. She called the screening they all went through "a joke."

“Am I allowed to tell you that?” she wondered, noting they were asked to fill out a form confirming they had no temperature or shortness of breath. “And then they just say ‘Welcome home!’ ”

While in Paris, they stopped by several tourist spots like the Eiffel Tower and the Louvre (before both closed Friday) without lines.

“Everyone was calm. Everyone was sharing,” Aimee said, noting the Europeans they encountered didn’t hoard toilet paper. “Then I got on Facebook and my heart rate started to go up. They’re nervous (in Europe) but it’s not in such a selfish, everyone-fend-for-themselves kind of way. To be the superforce of the world but be so scared all the time is kind of ironic.”

“My friends went to Colorado and they were so nervous to go to Colorado because of the coronavirus,” 9-year-old Lucy Bloom said. “And we were like, ‘We went to Europe.’ Nobody in France minds about the coronavirus.”

Tony Zubieta, 21, was studying abroad in Madrid but flew in to Dallas/Fort Worth International after Texas Christian University mandated all students to come home. He was grateful he made it Sunday when a flight attendant told him that as of tomorrow, Madrid flights couldn’t come back. His mom is in her 60s and worried he’ll give it to her, so she booked him a hotel room in Fort Worth for a week.

“Madrid was scary, I’m not going to lie,” said Zubieta, as he watched number of cases tick up. Before heading back to the U.S., he was eating what he had left because grocery stores had emptied out before closing altogether. “We were just counting our days to come back home, it was getting so bad.”

Madrid ran out of masks and sanitizer, so Zubieta bought a mask in Copenhagen to save for his flight home.

He was surprised how smooth deplaning was and how much DFW was “really shut down.”

The scene Sunday at Detroit Metro Airport was one of seeming calm as far fewer passengers than usual arrived.

At Detroit Metro's international terminal, more than a dozen passengers said they encountered no major health concerns after arriving from Cairo, Egypt; Frankfurt, Germany; Tokyo, Japan; and Manila in the Philippines. And airport officials have not had complaints about long lines awaiting customs screening, said Erica Donerson, vice president for communication and external affairs for the Wayne County Airport Authority.

After flying direct to Detroit from Frankfurt, Meghan McMichael, 16, wore a face mask on Sunday afternoon as she awaited ground transportation home to Hudson, Wisconsin, a distant suburb of Minneapolis.

McMichael's nine-hour flight brought the German-speaking, high-school sophomore back stateside from studying abroad for a semester, a plan cut short by the pandemic. "The flight attendants were taking bets on how long it was going to take” before she and others were allowed to get off the aircraft after customs and immigration boarded. ”But it took seven minutes, maybe? It was really quick."

The teen was one of the first to step off, after flying stand-by and snaring a first-class seat on the sparsely filled flight. "Once all this calms down, I really hope to go back" to Germany, she said.

Roesli Arena, a student at Boston University, was scheduled to fly back Saturday through London from a spring break trip to Switzerland, but rescheduled a direct flight to Newark on the advice of Massachusetts Sen. Ed Markey's office, who told her she otherwise could be subjected to a 14-day quarantine in the U.K.

"The flight was pretty full and somewhat normal," Arena said. She and other passengers were given a form from the CDC to provide information on travel history and any relevant symptoms. After landing, the plane was stationed at the gate for almost three hours before passengers were let off in groups of 20 to be screened. "They quickly took all of our temperatures using a no-touch thermometer."

The situation was so bad at O'Hare that Illinois Gov. J.B. Pritzker called out the Trump administration on Twitter, and the airport tweeted that the problem stemmed from a lack of staffing. Chicago police distributed bottled water and snacks to travelers waiting to get through the lines.

"To the frustrated people trying to get home, I have spoken with the (Chicago) mayor and our senators and we are working together to get the federal government to act to solve this,'' Pritzker wrote Saturday evening. "We will do everything within our power to get relief."

Laken James of Green Bay, Wis., who flew into O'Hare from Frankfurt, Germany, had a different experience, calling the screening process "super-organized."

James and "probably everyone on my flight" were put into a "really small room" and were told to fill out a sheet of paperwork entailing all locations visited before taking a "simple temperature check."

Airport officials recommended everyone self-quarantine, James added.

Regan Penn from Antioch, Illinois, who flew in from Amsterdam, concurred.

"It was like a 20-minute wait, just to get the form filled out, Penn said. "They just asked anyone coming from China, Iran or any of the Schengen countries additional questions. Took your temperature and then ‘OK, bye.’ "

Pritzker said Sunday on NBC's "Meet the Press'' that the government should have added more customs and CDC staffers to handle what everyone expected would be a surge in passengers rushing home because of the restrictions.

"So last night, as people were flooding into O'Hare Airport, they were stuck in a small area, hundreds and hundreds of people. And that's exactly what you don't want in this pandemic."

By Sunday afternoon, the situation seemed to be improving at O'Hare, with many travelers reporting waits of less than 30 minutes.

Houston resident Jennifer Barber said it took 25 minutes to clear customs from the time she landed in Chicago.

"No lines or anything,'' she said. "It was really efficient.''

Barber, who flew in from the Czech Republic via London, said her temperature was taken several times and she was eventually asked to wear a mask because she has a "little cough.''

Vees Kujda didn't have any complaints about long lines but he was angry about having to re-route his travel through Chicago because his initial destination, Tampa, didn't have the required airport screening.

Kujda, who lives in Chicago, said he didn't find out until he showed up at London's Stansted Airport and was told he had to buy a new ticket and fly out of London Heathrow to Chicago.

The new ticket cost him $1,500 and he had to book a hotel near Heathrow. All for what he called a less-than-thorough screening.

“Totally unprepared,'' he said of the new restrictions. "Wasted thousands of dollars for a 15-minute screening. If you want to really do a screening, then do the right screening.”

President Donald Trump weighed in on the long lines Sunday afternoon. He tweeted that the government is "moving as quickly as possible'' but said it's "very important that we be vigilant and careful.'' He called the airport medical screenings "very precise.''

Customs head Morgan said in a statement Sunday on Twitter that the long lines were unacceptable but he stopped short of saying they would disappear.

"With this national emergency, there will be unfortunately be times of disruption and increased processing time for travelers,'' Morgan said. "CBP is working around the clock to minimize these inconveniences.''

Homeland Security chief Wolf acknowledged the long lines late Saturday and said the government was working to add additional screening capacity to speed things up.

Without extra staffing, the mess is likely to get worse because of a broadened ban Trump announced Saturday.

Beginning early Tuesday, passengers on flights from England and Ireland will join the lines for enhanced screening upon arrival.

Contributing: Nancy Armour, Nicquel Terry Ellis, Jori Epstein, Robert Hanashiro and Hannah Yasharoff, USA TODAY; Bill Laitner, Detroit Free Press; and Anne Brennan, Wicked Local