Long lines of returning international passengers at some US airports have prompted harsh criticism of the Trump administration after the President announced a ban on all travel between the US and Europe amid the coronavirus pandemic.
State and local officials have raised concerned that the queues could have turned travellers waiting in line into Covid-19 carriers as they tried to get home.
About 3,000 Americans returning from Europe waited in line at Chicago's O'Hare International Airport to be screened, with some social media users suggesting the wait was upward of four hours.
Illinois governor JB Pritzker and Chicago mayor Lori Lightfoot - both Democrats - said the scenes violated federal recommendations that people practice "social distance" amid the outbreak.
Ms Lightfoot took aim at vice president Mike Pence and his coronavirus task force, she said Mr Pence had not discussed with local officials before implementing the screening program.
"Thousands of travellers were forced to wait in exceedingly long lines, congregating in concourses and putting themselves and their loved ones at greater risk of exposure," Ms Lightfoot said.
Under the new measures, passengers were screened by federal customs and homeland security agents for symptoms of the virus before they were allowed to leave the airport.
Long lines also formed on Saturday in Boston, Dallas and others of the 13 US airports still accepting return flights from Europe.
Texas governor Greg Abbot - a Republican and strong supporter of the president - tweeted on Sunday that the lines in Dallas were "unacceptable" and said he was "working hard" to resolve the issues.
President Donald Trump defended the administration's actions in a tweet on Sunday.
He wrote: "We are doing very precise medical screenings at our airports.
"Pardon the interruptions and delays, we are moving as quickly as possible, but it is very important that we be vigilant and careful. We must get it right. Safety first!"
Acting Customs and Border Patrol Commissioner Mark Morgan said in a statement on Sunday that the agency was making improvements to its procedures, but that it must "balance our efficiencies with ensuring the health and safety of all American citizens through enhanced medical screening".
The latest death toll from coronavirus in the United States has climbed to 61, while the country reached nearly 3000 confirmed cases.