Does the U.S. need federal air marshals?

WASHINGTON -- America's federal air marshal program has come under attack in Congress, with suggestions that the program is wasteful and unnecessary.

But defenders say it's the air marshals who are keeping us safe when we fly.

The air marshal program ramped up just after 9/11, before cockpit doors were reinforced, watch lists expanded, body scanners added to airports and stricter restrictions on what you could bring on board an airplane. That has some lawmakers wondering how much do federal air marshals contribute to keeping travel safe?

In a January review of the Department of Homeland Security, outgoing Sen. Tom Coburn wrote, "It is unclear to what extent the...program is reducing risk to aviation security."

Also unclear, wrote the senator, is if the "program and its strategy for allocating resources, including assigning federal air marshals to certain flights, has kept pace with these changes and security enhancements"

"I would like to see it totally eliminated. Totally defunded," says Republican Rep. John Duncan of Tennessee, the air marshals' biggest critic. "I think it is the most needless, useless federal agency in the entire federal government and that is really saying something because there is a lot of waste and inefficiency in the federal government."

Duncan sits on the House Oversight Committee where in September the agency disclosed three air marshals in Chicago stand accused of hiring prostitutes, posing as porn producers and recording at least one encounter on a government phone.

And last year the agency's former director, Rober Bray, retired as allegations swirled he used his position to purchase discounted firearms.

"There have been threats to the airline industry from ISIS and al Qaeda and other Islamic fundamental groups since 9/11. So I can't say that we're any safer, therefore the program is just as valid as it was then," says Jonathan Gilliam, a former air marshal.

Gilliam acknowledges the agency has been plagued by low morale and high turnover. A 2014 report ranked the TSA near the bottom of the list for worker morale, but he says the fact the job may include hours of boredom doesn't mean it's unnecessary.

"We saw in 9/11, you can take that plane and kill thousands. So, you know, we can't base whether or not that small moment in time where that door is open is worth billions," Gilliam says. "I think we have to look at it as, how do we secure that moment in time.... You do not know how many people did not try to take over a plane."

The Department of Homeland Security refused to answer questions about how many arrests federal air marshals make and declined CBS News' request for an on camera interview.

In a statement, DHS says "Federal air marshals... are an integral part of our risk-based security and are the last line of defense on board an aircraft."