U.S. airlines expect a surge of international travelers when the United States reopens to fully vaccinated visitors Monday. The Biden administration announced the new guidelines in September and set Nov. 8 as the day the borders open.

"Delta (DAL) has seen a 450% increase in international point-of-sale bookings versus the six weeks prior to the announcement," the airline stated in a press release that predicts many international flights will be 100% full and stay that way for several weeks.

The new guidelines require non-citizen travelers to provide proof they have been fully vaccinated against COVID-19 prior to boarding a flight to the U.S. All passengers, including U.S. citizens, will be required to test negative for COVID-19 within three days of a flight's departure.

Delta Flight DL106 from Sao Paulo Brazil will be Delta’s first international flight to touch down in the U.S. under the new rules when it lands in Atlanta Monday morning. That will be the start of a return to business which Delta predicts will include 25,000 passengers boarding its 139 flights to the U.S. later that day.

Delta CEO Ed Bastian recently told Yahoo Finance the airline expects to end the year with roughly 75% of its business restored compared to 2019. He praised the Biden administration's move to allow foreign travelers back into the country as a step that will help reunite families and improve the top and bottom lines of Delta's balance sheet.

"Restoring the remaining one-third of our revenue base is dependent on further business and international demand improvement," Bastian told investors during the Q3 earnings call.

Tools to make international travel easy

Delta is launching its "FlyReady" tool within the airline's app to help passengers upload their vaccine and test records. Other airlines like United (UAL) are also offering tools, like its Travel-Ready Center, to make international traveling easier.

The loss of international travelers hit United especially hard. "During the pandemic, United's geography has been a greater headwind than any other U.S. airline, given our largest business coastal hub and international exposure," CEO Scott Kirby said.

Raymond James analyst Savanthi Syth told Yahoo Finance the airline has the most to gain with the return of international travel because 50% of United's revenue, in 2019, was tied to international trips.

"If you look at their 2019 revenue, about 60% of their revenue was domestic 40% International. But of that 60%, about 10 percentage points were domestic trips related to an international trip. So really 50, they're about 50-50, domestic International," she said.