But a CBS News investigation has found the agency is fighting a battle not just up in the air but in its own backyard as well.
"How would you describe the management in the air marshal service?" CBS News chief investigative correspondent Armen Keteyian asked a current air marshal.
"Sexist, racist, homophobic, anti-disabled vet group, grossly incompetent," said the marshal, whose identity was concealed. "That's the general consensus among air marshals."
Nearly two dozen current or former marshals have told CBS News the agency is dominated by an "old boys club" of white, male supervisors -- mainly ex-secret service agents who, they allege, routinely discriminate, intimidate and retaliate against employees who question their actions or authority.
"This behavior has just spread like a cancer and it's out of control," the marshal said.
There are, on average, more than 23,000 domestic flights and nearly 4,000 international flights coming in and out of the U.S. every day and just about 3,000 air marshals to cover all those flights.
"As an agent, your job is to basically prevent planes from flying into buildings, protect the aircrafts. And the culture of this management was to demean and demoralize their agents rather than support them," said Craig Sawyer, a former air marshal.
And the lawsuits, records and other material we discovered depict a hostile work environment in field offices nationwide.
More on Air Marshals from Pro Publica
In New Jersey, a female air marshal contends she was told "women don't belong here."
In Chicago, two marshals charge they were fired after complaining their supervisors used racial slurs.
In Cincinnati, six air marshals say they were harassed based on age, race and physical disabilities.
And a photo obtained by CBS News shows a board posted in a field office in Orlando. It's set up like the game show "Jeopardy" where, it's alleged, managers used derogatory code words to refer to groups who would be harassed or get undesirable assignments - including homosexuals, African Americans, veterans and others. The TSA is investigating.
"This affects every American citizen because their tax dollars are being wasted, and their protection is being squandered," Craig Sawyer said.
Sawyer is a former air marshal manager and a decorated combat vet. He says this kind of culture has crippled the agency.
"There are thousands and thousands of flights that are unprotected because good agents have been chased off," Sawyer said.
That may be why, as one internal email shows, the service recently sought help from six other federal agencies -- like the Coast Guard -- in order to meet a "90-day [TSA] surge initiative" to increase security on U.S. flights in response to the attempted Christmas day attack.
The Federal Air Marshal Service declined to speak with CBS News on camera. But in a statement late today the service said is "dedicated to …fostering a diverse and inclusive workplace…" and has a "…policy of zero tolerance of harassment, discrimination, or retaliation in the workplace."
Homeland Security Director Janet Napolitano oversees the service.
"We want our air marshals to feel that they are treated well and we will work with them on resolving certain issues," Napolitano said.
But that's little consolation to air marshals who are seeing more and more problems in an agency that's supposed to prevent them.