Flight 722 which left Philadelphia just before 9 p.m. Monday was scheduled to land in Dublin, Ireland early Tuesday morning.
However, just after 10 p.m. the plane made an emergency landing at Boston's Logan International Airport.
In response to a passenger's tweet questioning what happened, American Airlines wrote on Twitter, "We're sorry for the unexpected stop. We'll be letting someone off the plane in BOS and we'll have you on your way."
The female passenger was originally described as unruly by American Airlines in a statement:
American Airlines Flight 722 from Philadelphia to Dublin was diverted to Boston due to an unruly passenger. Law enforcement met the plane upon its arrival in Boston. We're working to get our customers to Dublin as quickly as possible, but the safety and security of our employees and customers are always our top priority.
However, later on in the night, Massachusetts State Police said the passenger suffered a possible medical issue. They say her husband had to restrain her.
State Police continue to investigate.