Airlines and other travel-industry groups asked the Biden administration on Wednesday to drop Covid test requirements for vaccinated passengers before U.S.-bound flights, a bid to invigorate the sluggish recovery in international travel.

“Doing so is justified by the pervasiveness of COVID cases in all 50 states, increased immunity and higher vaccination rates as well as new treatments,” said an industry letter to White House coronavirus response coordinator Jeffrey Zients, which was seen by CNBC. “Removing the requirement will greatly support the recovery of travel and aviation in the United States and globally without increasing the spread of COVID-19 and its variants.”

The letter was signed by Airlines for America, a lobbying group that represents Delta, American, United, Southwest and others, along with more than two-dozen other industry associations representing airlines, hotels, airports and aircraft manufacturers.

The Trump administration in January 2021 established a policy requiring inbound air travelers, including U.S. citizens, to show proof of a negative Covid test taken within three days of departure.

The Biden administration in December tightened rules to require travelers to show tests taken within one day of departure after omicron cases surged. That change came a month after the U.S. ended a broad travel ban on visitors from Europe, China, Brazil, India and the U.K.

International travel demand, however, continues to lag domestic leisure, which helped airlines recover from record losses in 2020.

The groups argued in their letter that testing requirements for vaccinated individuals is too onerous and deters travel. The U.K., starting Feb. 11, will drop its Covid testing requirement for vaccinated arrivals.

International inbound air travel won’t likely recover to pre-pandemic levels until 2024, Roger Dow, president and CEO of the U.S. Travel Association, an industry group, said during a call with reporters earlier Wednesday. That is “leaving a tremendous amount of ground to make up.”

Throughout the pandemic, airlines and travel groups have repeatedly pressed both the Trump and Biden administrations to loosen restrictions that they have said prolonged a slump in long-haul international travel.

European countries began lifting entry bans on visitors from the U.S. and other countries last spring, a move that wasn’t followed by the U.S. until November.

The White House didn’t immediately comment on the letter.