https://www.siliconvalley.com/2020/05/28/elon-musks-boring-co-proposes-tunnel-to-ontario-airport-as-alternative-to-light-rail/

Elon Musk’s The Boring Co. proposes digging a 2.8-mile underground tunnel linking Rancho Cucamonga with Ontario International Airport as an alternative to extending a light-rail system from Pomona, San Bernardino County transportation officials said.

The sub-surface people-mover project would be the first of its kind in San Bernardino County and could replace stalled plans to construct an above-ground extension of the L Line (formerly Gold Line) light-rail that currently ends in Los Angeles County. Other projects on a preliminary list of alternatives to the L Line include a zero-emission train from a Metrolink Station off the San Bernardino Line or a connection from the Riverside Metrolink Line, which has a stop south of Ontario airport.