Citing security concerns, three House of Representatives lawmakers introduced a bill Tuesday to block flights between Cuba and the United States just ahead of the scheduled plans to resume daily flights between the countries.

The lawmakers — Reps. John Katko, a New York Republican; Richard Hudson, a North Carolina Republican; and Henry Cuellar, a Texas Democrat — have expressed concerns that the direct flights from Havana into the U.S. would make it easier for terrorists to board them. As a part of the diplomatic thaw between Cuba and the U.S., a number of daily flights between the nations are scheduled to begin in September. 

The Transportation Security Administration (TSA), a part of the Department of Homeland Security, has to certify Cuban authorities are up to U.S. standards for screening passengers and luggage before direct flights begin, according to USA Today. The TSA is working on its review of Cuban airports. 

The proposed legislation comes just one week after the Department of Transportation selected eight U.S. airlines to start up scheduled flights between Cuba and 10 U.S. cities: Atlanta, Charlotte, Ft. Lauderdale, Houston, Los Angeles, Miami, Newark, New York City, Orlando and Tampa.

The bill looks to mandate the TSA to certify that Cuba has the proper screening equipment and airport worker training — meaning everything is up to U.S. standards — before direct flights can begin. The bill also seeks to secure an agreement allowing air marshals onto flights. Marshals fly undercover and are armed.

Katko has repeatedly expressed concerns over Cuban airport security, reported the Syracuse media group. "You’ve got a potential nightmare on your hands," said Katko, via USA Today. "I’d rather have inconvenience than a tragedy."

The Syracuse Congressman said Homeland Security officials have noticed an uptick in Cuban passports appearing in the Middle East and Afghanistan. He is also concerned suspected terrorists could find entry into the U.S. through lax Cuban airport security. 

"It may turn out there is nothing to worry about, but we don't know," Katko said to reporters. "So that's the concern that we have."