A federal complaint was filed Monday against a Southwest Airlines co-pilot accused of operating a plane under the influence of alcohol.

Carl Fulton, 41, made an appearance before U.S. District Judge Paul Warner Monday.

Fulton was charged with one count of operation of a common carrier under influence of alcohol or drugs. The charge carries a maximum penalty of 15 years in prison and up to $250,000 in fines.

Fulton was pulled from the cockpit of a Southwest Airlines Flight preparing to leave Salt Lake City bound for Phoenix with 123 passengers on board at 8 a.m. Sunday after a Transportation Security Administration screener detected alcohol on his breath.

The screener followed Fulton and watched him board Flight 136, a Boeing 737. Airport police were called and Fulton was asked to step outside the plane, according to a complaint filed in federal court.

"Pilot Fulton acknowledged very politely, 'Yes, sir,' that he understood the accusation. Pilot Fulton stated, 'Do what you have to do,'" according to court documents.

Initially, Fulton said that he had just a beer the previous night, he stopped drinking by 10 p.m. and he refused a breath test, according to court documents.

When informed the FBI was now investigating, Fulton submitted to the breath test. His blood alcohol content was 0.039 approximately one hour after being pulled from the cockpit, court documents state. A second test registered his blood-alcohol content at 0.038.

Under federal statute, a pilot is presumed to be under the influence if his or her blood-alcohol content is at 0.10. But U.S. Attorney Stephen Sorenson noted that mark was only a presumption and not a set standard. A pilot can also be charged if he is simply assumed to be under the influence of alcohol.

Sorenson said other tests can be used to determine if a person is under the influence other than a breath test. But he declined to comment on other possible evidence in Fulton's case.

It is a crime under Utah State Code to operate an aircraft with a blood-alcohol content of 0.04 or higher, the same standard as the FAA. The limit in Utah for driving a car is 0.08.

FAA regulations also require eight hours "from bottle to throttle," meaning a pilot cannot fly within eight hours of having any alcohol. Even if a pilot's alcohol content is at 0.02, FAA rules require that pilot to be grounded for eight hours.