Testing, testing, 1, 2, 3.

Airline executives who run some major carriers in the U.S. are speaking out against a possible coronavirus testing requirement for domestic travel, arguing it would diminish already-weak demand and take away valuable testing from those who need it for medical reasons.

Earlier this week, a CDC official said that the Biden administration is considering implementing mandatory coronavirus testing for travelers on domestic flights in the U.S. (iStock)

Earlier this week, Dr. Marty Cetron, director for the Division of Global Migration and Quarantine at the Centers for Disease Control and Prevention, said that the Biden administration is considering implementing mandatory coronavirus testing for travelers on domestic flights across the country.

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The requirement would expand upon the U.S.’ new international testing requirement, which took effect Tuesday. As of Jan. 26, all travelers bound for the U.S. must test negative for COVID-19 within three days of boarding their flights or present proof of having recovered from the virus. No further details were released on the potential mandate for domestic travel.

Meanwhile, execs for American Airlines, Southwest Airlines and JetBlue Airways are already pushing back. On Thursday, the trio of airlines announced they lost a combined $3.5 billion in the last three months of 2020, The Associated Press reports.

"Travel restrictions on international have resulted in a reduction in demand," American Airlines CEO Doug Parker said. (iStock)

"Travel restrictions on international have resulted in a reduction in demand," American Airlines CEO Doug Parker said during a fourth-quarter earnings call. "We have seen that particularly on the short-haul international travel, things like Mexico and the Caribbean."

Though the airlines support testing international travelers in the fight against COVID-19, they say that testing travelers moving within the U.S. is expensive and impractical.

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Though the airlines support testing international travelers in the fight against COVID-19, they say that testing travelers moving within the U.S. is expensive and impractical. (iStock)

"Why pick on air travel?" Southwest CEO Gary Kelly asked in an investor call. "If you want to test people, test them — but test them before they go to the grocery store, test them before they go to a restaurant."

JetBlue President Joanna Geraghty stressed that COVID-19 testing would be better allocated to those who need it for medical reasons.

("Frankly, we're concerned that it would actually reduce the ability of some people who legitimately need to get tested for health reasons to get tested," said JetBlue President Joanna Geraghty. (iStock))

"In many parts of the country, testing slots are scarce and it takes, frankly, many days and some cases actually get results back," Geraghty said during an earnings call. "And so when you start thinking about a framework that's already overburdened, and you add domestic travelers into that, this puts a ton of pressure on an already fragile system and, frankly, we're concerned that it would actually reduce the ability of some people who legitimately need to get tested for health reasons to get tested."

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American, Southwest and JetBlue all also issued dismal revenue outlooks for the current quarter, echoing similar sentiments from Delta, United and Alaska. The Associated Press reports that the new year is off to a "grim start" for the six biggest U.S. airlines, which lost $34 billion last year.

As demand for travel remains weak, and likely will for several more months, airlines continue to cut costs and encourage employees to leave. Federal aid has also averted more furloughs, at least until March. Meanwhile, airlines short on revenue are staying afloat with billions of dollars from private lenders and taxpayer-funded relief.

Fox News’ Daniella Genovese and The Associated Press contributed to this report.