A 29-year-old man who struck a flight attendant and tried to open the cockpit door during a flight to Florida has pleaded guilty to interfering with a flight crew and could face up to 20 years in prison.

Prosecutors said that passengers noticed that Kameron C. Stone of Fairfax, Virginia, smelled strongly of alcohol, refused to stay in his seat, and pretended to shoot a gun at passengers during a United Airlines flight from Dulles airport in Virginia to Pensacola, Florida, last April.

As the plane began to descend for landing, Stone tried to open the cabin and cockpit doors. When a flight attendant attempted to stop him, Stone grabbed her shoulders and shoved her into a wall, bruising her chest, face, arm, and shoulder, according to court documents.

Three passengers, including an off-duty federal marshal, restrained Stone, and three mini-bottles of vodka fell from his pocket during the tussle, according to prosecutors. Police met the plane when it landed.

Sentencing was scheduled for April 28 in federal district court in Pensacola, Florida. The maximum sentence for interfering with a flight crew is 20 years, and Stone also pleaded guilty to assault in an aircraft, which carries a one-year maximum sentence. He could get less under federal guidelines, however, and both sides said they couldn’t predict the sentence.

Unruly passengers have become a bigger problem since the start of 2021. The Federal Aviation Administration said this week that it has received 394 complaints from airlines this year after getting nearly 6,000 last year. Most of the incidents are related to passengers not wearing face masks, and alcohol is involved in many cases.

Last week, Delta Air Lines CEO asked the US federal government to create a new no-fly list for passengers who disrupt, similar to a federal list for people on a terrorism watch list.