Southfield, Mich. ? A Michigan woman who fell asleep on a United Express flight to Philadelphia says she woke up and was shocked to find she was alone on the plane.

Ginger McGuire said no one had awakened her when the plane landed more than three hours earlier.

She said she paced the aisle for about 15 minutes early Tuesday until the locked door opened and police demanded identification.

“Waking up to an empty airplane and not being able to get out — it was very horrifying,” McGuire, 36, told reporters Thursday as her lawyer announced a lawsuit.

McGuire said she simply fell asleep after a long trip that stretched from Detroit to suburban Washington and, finally, Philadelphia.

United Airlines spokeswoman Sarah Massier declined to comment because the incident has led to a lawsuit.

A message seeking comment was left at Trans States, based in Bridgeton, Mo. The Transportation Security Administration said it was investigating.

The United Express flight is operated by Trans States Airlines in partnership with United Airlines.