East Ontario appears closer but is still 3 miles from the airport by road according to google maps. I don't know if that is to the entrance to the airport or the terminal. The darn runways get in the way or it would be much closer. So there are stations in the general vicinity but nothing you can begin to walk w/ luggage.That's incorrect. The Metrolink Riverside Line stops at East Ontario station which is located on the southeast side of airport. Unfortunately, there's no access to the terminal. You'll have to call the taxi to pick you up.Metrolink doesn't stop in Ontario. The San Bernardino line stops in Upland, which looks to be about 4 miles from the airport. However, there are some freight tracks that are just north of the airport that perhaps could be utilized to provide service to the airport. I don't know a thing about them.
Upland is a little too far, use Rancho Cucamonga station. There's an Omnitran bus (one transfer) will take you there, but it's not convenient.
Rancho Cucamonga is 4.5 miles so not much help there. So appears all of them require a bus or a taxi to finish off the journey.
Thanks for the information re Riverside line. I thought that dipped more to the south for some reason.
Dan