David Arntson, 60, pleaded not guilty in federal court in Los Angeles on Tuesday afternoon, said Thom Mrozek, a spokesman for prosecutors. An attorney for Arntson declined further comment.

Arntson was arrested on Jan. 20 and arraigned in Los Angeles, according to the U.S. Attorney for the Central District of California.

The charges stem from two flights on Alaska Airlines, a unit of Alaska Air Group Inc, on June 20, 2014, according to prosecutors. Arntson flew from San Diego International Airport to Portland International Airport in Oregon, and then flew from there to John Wayne Airport in Orange County, California.

It is not known how many passengers were on the flights. Alaska Airlines exclusively flies Boeing Co 737s.

After landing on his last flight, Arntson was selected for a random drug test, according to prosecutors. Separate tests found the California resident had a blood-alcohol concentration of 0.134 percent and 0.142 percent.

Under federal law, a person operating a commercial airliner is deemed “under the influence” if his or her blood-to-alcohol level is at or above .10 percent.

The charge carries a maximum penalty of 15 years in federal prison. Arntson was released from custody on a $25,000 bond, prosecutors said.

When Arntson saw the drug tester after he landed in Orange County, his co-pilot recalled him saying, “I bet it’s for me,” according to the criminal complaint filed by prosecutors last month.

Following the drug test results, Alaska Airlines removed Arntson from duty. The Seattle-based carrier said he refused to submit to an investigatory interview.

“Mr. Arntson left the company before we were able to complete an investigation that would have led to his termination,” the airline said in a statement last month.

It is unclear exactly when Arntson left the company. Alaska Airlines declined comment on Wednesday.

A trial is set for April 5, and a pre-trial conference is set for March 28.