US airlines bet on pent-up demand, mass vaccinations in rebuilding summer schedules

As airlines emerge from the worst period in commercial aviation history, U.S. air carriers are rebuilding their networks and adding dozens of new destinations.

Despite Centers for Disease Control and Prevention guidelines against travel, U.S. airlines say pent-up demand and mass-vaccination is drawing the highest number of reservation searches in a year. This comes as the Transportation Security Administration reports it screened more than a million passengers a day since March 11.

United Airlines announced it will fly 52% of its 2019 schedule this summer -- the carrier adding 26 new non-stop routes to coastal vacation destinations taking off Memorial Day Weekend.

"In the past few weeks, we have seen the strongest flight bookings since the start of the pandemic," Ankit Gupta, vice president of United's domestic network planning and scheduling, said in a press release. "As we rebuild our schedule to meet that demand, adding in seasonal point-to-point flying is just one of the ways we are finding opportunities to add new and exciting service."

The new service includes flights from Midwest cities like Cleveland, Cincinnati and Milwaukee to destinations like Hilton Head, South Carolina; Pensacola, Florida; and Portland, Maine.

American Airlines also announced it will add 10 new, returning and seasonal routes from Austin.

"These routes not only provide opportunities for companies to get back to business and for leisure travelers to enjoy the excitement of Austin, but also connect Central Texans with new leisure destinations they desire," Brian Znotins, American’s vice president of Network Planning said in a press release.

In May, American Airlines will fly 80% of its 2019 May schedule. The carrier will introduce 18 new routes for the summer season, including six new routes from John F. Kennedy Airport in New York to Latin America and the Caribbean.

"We're optimistic for the summer of 2021," Julie Rath, American Airlines vice president of customer experience, said in an interview with ABC News. "So we're optimistic that we'll continue to see travel and especially leisure travel as we've been seeing recently, continue to increase."

Delta Air Lines announced it will introduce nine new routes and add flights to more than 20 leisure destinations this summer – the carrier said the move "follows renewed optimism and growing customer confidence in upcoming travel."

Destinations include service to Montana, Wyoming, South Dakota and Nevada. The carrier is also adding more flights to leisure markets like Hilton Head and Myrtle Beach, South Carolina, and various Caribbean destinations.

On the international front, Delta announced Friday it will offer more service to Iceland this summer. This comes as the country announced it will open its borders to vaccinated Americans. Customers traveling to Iceland will be required to provide proof of full vaccination or recovery of COVID-19.

"We know our customers are eager to safely get back out into the world, including exploring one of the globe’s most beautiful outdoor destinations," Joe Esposito, senior vice president of network planning, said in a press release. "As confidence in travel rises, we hope more countries continue reopening to vaccinated travelers, which mean more opportunities to reconnect customers to the people and places that matter most."

Carriers are not only adding new routes to their bolster their schedules, but also making it easier for customers to book hotels and transportation once they arrive to their destinations.

JetBlue launched a new travel website to assist its customers in booking hotels, car rentals and activities. The service, called Paisley by JetBlue, will help the airlines customers by "using flight information to make individually tailored suggestions for travel components such as hotel stays and car rentals."

Similarly, American said it has enhanced its travel planning tool "to help customers make informed decisions on where to travel and what to expect upon arrival." The tool provides customers with an interactive map that highlights the latest COVID-19 travel guidelines for various destinations.

While the CDC is still warning against travel, more than two dozen travel groups are urging the Biden administration to come up with a plan by May 1 to "safely reopen international travel" for this summer "if vaccine distribution and epidemiological trends continue in a positive direction."

The coalition called for the plan to include guidance that vaccinated adults can travel as well as the development of uniform federal principles for COVID-19 health credentials better known as "vaccine passports."

"If nothing is done to lift international travel bans and bring back demand, the U.S. Travel Association estimates that a total of a 1.1 million American jobs will not be restored and $262 billion in export spending will be lost by the end of 2021," the groups wrote to COVID-19 Response Team Coordinator Jeff Zients.

ABC News' Mina Kaji and Sam Sweeney contributed to this report.