A Washington state man is facing up to 20 years in prison after he admitted to jumping over a beverage cart and trying to take off his clothes aboard an American Airlines flight, which had to be diverted.

Adam Alexander Williams, 33, of Auburn, Washington, pleaded guilty Thursday to interference with flight members and attendants, more than 5 months after causing a flight from Seattle to Charlotte, North Carolina, to land in Billings, Montana, according to U.S. Attorney’s Office for the District of Montana.

William will be sentenced at a later date. In addition to prison time, he also faces a $25,000 fine and three years of supervised release.

According to court documents, Williams was traveling to North Carolina on Jan. 9 when his behavior “turned erratic and escalated” mid-flight.

At one point, he yelled at no one in particular, “Where is Jamie Sanders?” He later jumped over passengers in his row and onto a beverage cart in the aisle.

“As he came off of the cart, he almost landed on a flight attendant and pushed her into a seat, knocking drinks and cups to the ground,” records stated. “He then began to run down the aisle of the aircraft.”

Williams’ behavior was said to have startled the flight attendant, who appeared “distressed and traumatized.”

Prosecutors said that another cabin crew member managed to calm Williams down and escort him back to his seat.

“About 10 minutes later, Williams began to act up again and screamed an obscenity,” the documents alleged.

Flight attendants then placed several U.S. Marines, who happened to be on the flight, in seats around Williams as a precaution. But a short time later, “Williams stood up and began screaming while taking off his clothes.”

At that point, the aircraft’s captain turned the plane around and landed in Billings so that Williams could be removed from the plane.

The 33-year-old has been released from custody pending his sentencing hearing, which is scheduled for Oct. 20.

The Federal Aviation Administration has reported that as of June 28, there have been 1,562 reports of unruly passengers, of which 520 called for investigations.

Last year, the agency investigated 1,099 incidents involving unruly airline passengers.