Antelope Valley Line

Since the beginning of service, Metrolink had plans to extend the line north to the Antelope Valley but these plans were expedited by almost 10 years following the 1994 Northridge earthquake.[5] The earthquake caused the collapse of the freeway connector of State Route 14 (the Antelope Valley Freeway) onto Interstate 5 (the Golden State Freeway) at the Newhall Pass interchange, forcing all traffic to use the parallel 2 lane truck bypass that was unaffected by the quake. With funding from the Federal Emergency Management Agency the Southern California Regional Rail Authority constructed an emergency extension of the line to Lancaster to help relieve the traffic bottleneck. The U.S. Navy Seabees construction battalion and crews from the L.A. County Public Works Department were able to construct the stations in just a few days, compared to the normal three to six months. Emergency stations in Lancaster and Palmdale were both built in just three days and Metrolink started operating trains one week after the earthquake struck. Over the next five weeks additional emergency stations were added in Sylmar/San Fernando, Vincent Grade/Acton and Santa Clarita (Via Princessa).[5][6] While most of the emergency stations have since been replaced with permanent stations, the Via Princessa station still uses the same platform built after the earthquake.

Saturday service on the Antelope Valley Line has been operating since 1999,[7] Sunday service was added in September 2007.[8] As of August 2013, weekend service has expanded to 6 trains on Saturdays and Sundays.[9] Arrivals at LA Union Station are timed allow passengers to connect with Amtrak trains and trains on Metrolink's Orange County and San Bernardino lines.[9]

Express service was added to the line in May 2011.[10] Two express trains operate in the peak commute direction between Palmdale and Los Angeles (one southbound train in the morning, one northbound train in the evening). Express trains are about 18 minutes faster than trains that stop at all stations.

On April 30, 2015, Metrolink announced it will be offering discounted fares to riders on the Antelope Valley Line beginning July 1, 2015 as part of a pilot program. The fare pilot program, which will be in place for six months following the program's launch, will include several new ticket pricing options for riders on the Antelope Valley Line. There will be a 25 percent reduction in fares on all ticket types for trips along the corridor from Los Angeles to Lancaster, with the exception of the Weekend Day Pass, which will remain at its current $10 fare. In addition, a new "station-to-station" fare will be introduced in which riders traveling during off-peak hours (9 a.m. to 2 p.m.) will be able to purchase a one-way ticket to travel between stations for $2 per station. This fare is designed to encourage local trips using Metrolink as an additional mobility option complementing local bus service.[11]

A new Burbank Airport–North station opened in 2018 to serve Antelope Valley Line passengers traveling to Hollywood Burbank Airport. The station is located near the intersection of San Fernando Boulevard and Hollywood Way, with a free shuttle bus for passengers to the airport terminal located approximately one mile away from the station site.[12]

In July 2019, additional late evening train service and bi-directional service were being considered.[13]