(CBS) — The state’s mass transit agencies say they are willing to go to the mat with the National Rifle Association over concealed guns aboard trains and buses.

The transit agencies say buses and trains should be no different from planes. It’s against federal law to carry a concealed weapon aboard a plane.

In a letter to Illinois House Speaker Michael Madigan dated Feb.14, the chief executives of the RTA, CTA, Metra and Pace, as well as the head of the Illinois Public Transit Association, representing downstate agencies, wrote that concealed guns aboard mass transit would set the stage for inescapable and catastrophic mass shootings.

“There is no question that a gun fired in a 45×10 area, like a crowded bus, would be catastrophic – whether intended or unintended,” the letter states.

RTA chief of staff Jordan Matyas said that no other major transit agency allows guns aboard its trains or buses.

“In New York, in LA, in every other major metropolitan city, you cannot bring concealed carry on, so this would be a drastic change,” Matyas said.

Matyas said Wednesday that the RTA has tried to work with the NRA on the issue, but Matyas said he has been told concealed-carry on Chicago’s trains and buses is “non-negotiable” and that a mass transit exemption would be a “deal breaker” in the attempt to craft a new law.

A three-judge 7th U.S. Court of Appeals panel, in a December ruling, gave the General Assembly 180 days to pass a concealed-carry measure. Illinois Attorney General Lisa Madigan has asked for a rehearing by the full 7th Circuit.

If no law passes, NRA lobbyist Todd Van Der Myde has said, “We win.”

He said earlier this month at a south side forum that in the absence of any measure passed by the General Assembly, concealed-carry would become legal for anyone with a valid firearm owner’s identification card, without exceptions for such places as government buildings, schools or hospitals.

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