(CNN) The union representing aviation police officers at Chicago's two airports is asking Mayor Rahm Emanuel to shore up security by allowing officers to carry guns.

The request follows a CNN investigation that found that hundreds of aviation police officers are not armed and have been told to "run and hide" in the event of an active shooter.

A longstanding policy prohibits those aviation police officers from carrying a gun even though they are certified law enforcement officers; about 300 of them work along with armed Chicago police, which is the primary law enforcement agency at both airports.

"The safety of the flying public that utilize the Midway and/or O'Hare airports, and the APOs (aviation police officers) who are an integral part of the security of these airports is at high risk for compromise," according to a January 4 letter to Emanuel from Matt Brandon, secretary-treasurer of Local 73 of the Service Employees International Union.

The "run and hide" training given to aviation police "is contrary to everything... taught in the Chicago Police Academy," Brandon wrote.

He also requested a meeting with the mayor.

A representative for the mayor's office told CNN the letter was being reviewed, and no response has been sent yet.

In addition, Brandon claimed that Chief Richard Edgeworth, who oversees the aviation police officers, and Department of Aviation Commissioner Ginger Evans are hampering security measures.

"Their ostrich approach to attacks on the flying public and the employees/personnel at Midway and O'Hare airports cannot be part of any rational security strategy," the letter stated.

Evans has strongly defended Edgeworth against the union's attempt to oust him in the wake of a no-confidence vote by aviation police officers last September.

Edgeworth did not respond to repeated phone calls and offered a "no comment" before walking away when a CNN reporter approached him last fall outside his office.

In a statement to CNN Wednesday, a spokesman for the aviation department cited numerous security awards for Chicago's airports and wrote, "The multi-layered security approach at O'Hare and Midway Airports is working to keep passengers, employees, and security officials safe. The close coordination between Aviation Security Officers, the Chicago Police Department, TSA, U.S. Customs and Border Control, and the FBI has a successful track record of keeping the airports secure."

"How does 'run and hide' give the APOs... a chance to defend the traveling public or themselves?" Brandon's letter asked. "How does 'run and hide' help those 'different agencies' stand and defeat an attack?"

He continued: "After seeing the CNN exposé on our unarmed APOs, and watching Chief Edgeworth 'run and hide' from dangerous camera-wielding reporters, it all made perfect sense."

The union says there are about 279 aviation police officers out of 309 budgeted at O'Hare and Midway airports. An additional 231 armed Chicago police officers and supervisors are also budgeted.