Ruiz, a California Democrat and a trained emergency room physician, offered his medical expertise when flight staff asked if there were any doctors on board to assist a traveler who was having a seizure.
The passenger turned out to be Lisa De Pasquale, a columnist for the conservative news sites Breitbart News and Townhall. She was later treated by emergency medical personnel at Phoenix airport while Ruiz caught a connecting flight to Palm Springs, Calif.
"I think they were close enough that the flight did not need to be diverted," said Ruiz spokesman Michael Ford, confirming the congressman's actions.
The incident was the second time Ruiz had aided an ill passenger since he was elected to Congress in 2012. In October, Ruiz helped a 60-year-old man who collapsed after takeoff aboard a flight from Washington to Dallas.