The airline says the flight from Seattle to Denver had just pulled away from the gate Thursday morning when the little stowaway was spotted. The 737 jetliner returned to the terminal and passengers and crew boarded another plane about 90 minutes later.
Airline spokeswoman Bobbie Egan says the plane won't be returned to service until maintenance workers make sure the rat didn't damage equipment or chew any wires - and an exterminator certifies the plane is rodent-free.
Egan says workers also are trying to figure out how the rat got aboard. She says in cold weather, "sometimes rodents can seek shelter in strange places."