Add Sen. Jeff Merkley, D-Ore., to the growing list of lawmakers who are fighting airlines’ decision to sell middle seats during the COVID-19 pandemic.

Merkley on Thursday introduced a bill that would ban the sale of middle or otherwise adjacent airline seats during the pandemic and require face masks on planes for the duration of the coronavirus crisis.

He was spurred to do so after boarding a crowded American Airlines flight July 2. The flight was crowded enough that Merkley tweeted a picture of himself, looking frustrated in a packed plane.

“@AmericanAir: how many Americans will die bc you fill middle seats, w/your customers shoulder to shoulder, hour after hour,” he tweeted. “This is incredibly irresponsible. People eat & drink on planes & must take off masks to do so. No way you aren’t facilitating spread of COVID infections.”

In a news release announcing the bill’s introduction, Merkley said it was “incredibly irresponsible” for airlines to fill planes to capacity.

“If taxpayers are going to bail out airlines because they provide an essential service, it is not too much to expect the airlines not to make the pandemic worse,” he said.

Merkley’s bill would codify guidance the departments of Transportation, Homeland Security and Health and Human Services offered July 2, advising but not requiring airlines to block off seats or require face coverings to prevent the spread of the disease.

But lawmakers increasingly insist that government, not private industry, must lead in order to enforce public health guidance. Rep. Mark Pocan, D-Wis., wrote the CEOs of American and United Airlines July 8 to demand they practice social distancing while seating passengers.

“You both took a significant bailout from U.S. taxpayers this year to help your airlines,” he wrote. “Your thanks? You’ve decided to cram those same taxpayers like sardines into a twisted petri dish experiment to maximize your profits.”

And House Transportation and Infrastructure Chairman Peter A. DeFazio, D-Ore., in mid-May wrote trade groups Airlines for America and the National Air Carrier Association to urge them to maintain one seat width between passengers.

“Who among the CEOs of A4A carriers would want a member of their own family to be assigned to a middle seat between two potentially contagious passengers during the middle of a global pandemic?” he asked, referring to Airlines for America.

Not all airlines are allowing passengers to book middle seats.

Delta Airlines on June 26 announced it would block the selection of middle seats and cap the number of seats booked in every cabin through Sept. 30. Southwest’s website said it is holding middle seats open through at least Oct. 31, though customers can sit in middle seats if they’re traveling with family, for example. American and United are currently not limiting the sale of middle seats, though American had instituted limits on middle seat sales up until July 1.

‘Enhanced cleaning’

A spokeswoman for American declined to comment on Merkley’s bill but forwarded a message the company sent out just after July 4 saying in part: “We have multiple layers of protection in place for those who fly with us, including required face coverings, enhanced cleaning procedures, and a pre-flight COVID-19 symptom checklist — and we’re providing additional flexibility for customers to change their travel plans, as well. We know our customers are placing their trust in us to make every aspect of their journey safe, and we are committed to doing just that.”

Merkley’s bill would also bar any passenger or crew member from boarding a flight without wearing a mask. Airlines have increasingly required passengers to use masks on flights, and Southwest CEO Gary Kelly told CNBC Thursday morning he believed that the federal government should require masks for air travel and in public generally.

“You have to wear pants” in public, he said. “Why can’t we mandate that you have to wear a mask in a pandemic?”

Delta Airlines CEO Ed Bastian, meanwhile, told the Today show Wednesday that his airline has banned more than 100 flyers for refusing to wear face coverings.

“If you board the plane and you insist on not wearing your mask, we will insist that you don’t fly Delta into the future,” he said.