In a court motion filed Wednesday, Clayton Osbon's attorneys notified prosecutors their client will contend he was insane at the time of the incident.
Osbon is charged with disrupting a flight crew during a March 27 flight from New York to Las Vegas. He was eventually subdued by passengers but the plane had to make an emergency landing in Amarillo, Texas.
Osbon remains jailed in Texas awaiting a court-ordered psychiatric exam to determine his competency for trial and whether he was legally at the time of his breakdown. He was indicted last week by a grand jury.
The Associated Press contributed to this report.