An FBI affidavit said McKay, who began his air travel in Pittsburgh, became "aggressive" on United Airlines Flight 1108 to Portland International Airport.
According to the federal filing, McKay asked for four bottles of Jack Daniels whiskey before takeoff, but agreed to take only two bottles at a time.
One flight attendant told authorities that he grabbed her hand multiple times.
"As I served him, he grabbed my hand and said, 'I would like to keep you all night,'" the attendant reported. When she brought him his second set of drinks, he allegedly said, "I love you. Let me prove it to you. I'll make this guy next to me move. Sit next to me and I'll show you."
Flight crew also said that McKay approached them in the galley and started yelling toward the cockpit. Attendants smelled smoke on his person after he emerged from the lavatory.
The pilot told federal investigators that he almost diverted the flight to Denver, but decided against it when the man had passed out in his seat.
The incident marks the second time this month that an unruly passenger has landed in Portland. A Southwest flight from Seattle to Sacramento made an emergency landing in Portland when a man allegedly became "belligerent" and "confrontational" in mid-air.