­­­­­­­­­­­­­­­­­­­New preflight testing programs are allowing a small number of Americans to have a European Christmas holiday this year after all.

On Tuesday, Delta Air Lines launched a Covid-19 testing program for customers flying from Atlanta to Amsterdam, while a second program is scheduled to start on Saturday for Delta passengers flying to Rome.

Unlike other preflight testing programs being conducted by American and United Airlines, Delta's programs allow passengers to avoid quarantine requirements in Europe.

Three tests to Amsterdam, and four for Rome

Delta's new "Covid-tested flights" originate from Georgia's Hartsfield-Jackson Atlanta International Airport and will fly four times weekly to Amsterdam and three times weekly to Rome.

Passengers can avoid quarantines if they test negative for Covid-19 at varying intervals before and after the flight, including:

1. Five days before arriving in Amsterdam or up to 72 hours before departing to Rome (via PCR, or polymerase chain reaction test)
2. Before boarding the flight at Atlanta's airport (rapid test)
3. Upon landing in Amsterdam (PCR test) and Rome (rapid test)
4. At the airport before returning to the U.S. (rapid test, Rome's program only)

Notably, passengers must pass two PCR tests to avoid quarantining in Amsterdam. PCR tests, also referred to as molecular tests, are more accurate than rapid antigen tests but results can take days to process since they must be sent to a lab.   

In a press release published on Dec. 15, Delta said "once a negative result is received, customers will not need to quarantine." In response to a question about how long passengers must wait for their results, a Delta representative told CNBC's Global Traveler, "We would say most [PCR tests] take a few hours to get results."

The Delta representative also said passengers can wait for their test results in their homes and hotels.

Delta is talking to other governments about launching additional quarantine-free flights, including a New York to Rome connection, Reuters reported this week.

Italy's national carrier, Alitalia, on Dec. 8 started three weekly flights on that route which allow passengers to avoid quarantines if they present a negative Covid-19 test conducted within 48 hours prior to the flight or perform a rapid test at the airport before boarding.

Alitalia customers departing from the United States must also pass a rapid test upon arrival to avoid Italy's quarantine obligation.

Program eligibility

Delta's two preflight programs are available to "all citizens permitted to travel to the Netherlands or Italy for essential reasons, such as for certain specified work, health and education reasons," according to Delta's website.

Americans have been blocked from entering the European Union since it closed its external borders last March. The U.S. was not on a list of countries permitted to enter the EU starting July 1, a list which has since dwindled as countries have struggled to contain coronavirus outbreaks within their borders.

However, some travelers are able to enter the EU through exemptions, which include people who provide "an essential function or need" such as health care professionals and researchers, diplomats, military personnel, humanitarian aid workers and passengers traveling for imperative family reasons, among others.

Airlines aren't waiting for vaccines

Though vaccines are expected to help repair the badly tattered global travel industry next year, airlines are not waiting.

"The arrival of a vaccine is fantastic news, but it will take time for it to become widely available around the world," said Delta Senior Vice President Perry Cantarutti. "It's for this reason we have worked tirelessly with the authorities and our partners to create a blueprint for travel corridors that will enable air travel to safely resume." 

Steve Sear, Delta's executive vice president of global sales, said the company is focused on testing to revive travel.

"Carefully designed Covid-19 testing protocols are the best path for resuming international travel safely and without quarantine until vaccinations are widely in place," he said.

Covid flight risk? Depends who you ask

Delta is working with advisors from Mayo Clinic to implement the preflight testing program to Rome as well as safety standards on international flights.

"Based on the modeling we have conducted, when testing protocols are combined with multiple layers of protection, including mask requirements, proper social distancing and environmental cleaning, we can predict that the risk of Covid-19 infection — on a flight that is 60% full — should be nearly one in a million," said Henry Ting, Mayo Clinic's chief value officer.

Throughout the pandemic, the airline industry has tried to increase safety standards and instill confidence among potential passengers, with various experts and entities serving up statistics on the risk of infection that vary dramatically:

·       1 in 4,300 based on a full two-hour flight in the U.S. with everyone wearing a mask (a study by Arnold Barnett, professor at Massachusetts Institute of Technology)

·       1 in 7,700 if middle seats are vacant (Barnett, MIT)

·       1 in 1.7 million (Boeing)

·       1 in 27 million (International Air Transport Association)

IATA's figure was based on 44 known or suspected cases of inflight Covid-19 transmissions in some 1.2 billion flight passengers this year, a statistic that U.S. infectious disease specialist Dr. David Freedman called "bad math."

"One-point-two billion passengers during 2020 is not a fair denominator because hardly anybody was tested. How do you know how many people really got infected?" he told Reuters. "The absence of evidence is not evidence of absence."

IATA cited an article co-authored by Freedman in the Journal of Travel Medicine to support its data. However, the Sept. 25 article acknowledges that the "U.S. CDC has stated awareness of 1,600 cases on U.S. flights and 11,000 contacts within 2 rows but has not yet published in-flight transmission estimates" — a situation which "may be partly related to current economic or political circumstances."

At the article's conclusion, Freedman called the lack of large numbers of confirmed in-flight Covid-19 transmissions "encouraging but … not definitive evidence that fliers are safe."