LA/Ontario International Airport
Ride the Metrolink Riverside line to Pomona-Downtown or the Metrolink IE-OC and San Bernardino lines to Fontana. At either station, board the Omnitrans 61 (any 61- these are the termini of the line) and get off at the airport. Flag down a Long Term Parking shuttle at the Omnitrans stop, and you'll be taken directly to the terminal. One ride on the 61 is included in your Metrolink fare.
You can also ride Route 204 to the Ontario Mills mall, and board the 61 bound for Pomona there.
Take the San Bernardino line directly from downtown, or use the Omnitrans 215 to catch it in San Bernardino. For a cheaper (but slower) option from downtown San Bernardino, ride the Omnitrans 15 to Fontana Metrolink instead. This will also save you the roughly 1 mile walk between the bus terminal and Metrolink station in San Bernardino. Alight at Fontana and ride the 61.
Los Angeles International Airport
Ride Metrolink to Los Angeles Union Station, alight and board the LAX FlyAway bus service, which will take you directly to the airport via the freeway, non-stop. FlyAway stops at the Patsouras Plaza bus station at the east end of Union Station, and it costs
Note when trip planning: Check the FlyAway web site and do your trip planning manually. FlyAway is not in Google Transit. You can take a myriad of Metro bus and rail services between downtown and LAX, but FlyAway is universally faster,
Update: Commenters have noted that FlyAway is no longer the cheap way to travel, at $7. For a really, really cheap ride to LAX, check out my new post.
Burbank-Bob Hope Airport
Ride Metrolink to Burbank Airport station. You'll have to change trains at Los Angeles Union Station. On weekends, you will have to use the Amtrak Pacific Surfliner from Los Angeles. Do NOT buy an Amtrak ticket- your Metrolink ticket is good for passage to the airport on Metrolink or Amtrak trains. (On weekdays, you can also use the Surfliner if it's convenient.)
Santa Ana-John Wayne Airport
Weekdays, commute hours only:
Gary Hewitt at the City of Irvine graciously contacted me with information about his city's iShuttle system. iShuttle Route A provides direct service from the Tustin Metrolink to John Wayne Airport. The route is timed to meet each train, and will wait for late trains up to 15 minutes. You can catch it from morning IE-OC line trains 803, 805, 807 and 809, which leave Riverside-downtown at 5:11a, 5:41a, 6:16a, and 7:26a respectively. You can also catch it on evening IE-OC line train 813, leaving Riverside-downtown at 3:27p. The iShuttle is in Google Transit, for your trip planning convenience, and transfers from Metrolink are free. Normal cash fare is $1.00.
All other days & times:
Either ride Metrolink to Anaheim Canyon or the 149 to the Village at Orange. Pick up the #71 on Tustin Ave. and enjoy the hour-long ride. The 71 will get you as far as Main & Red Hill- you can either walk the 1.4 miles to the terminal, or pick up a #76 here that will take you to the airport. Either way, the 30-minute walk or the 20-minute wait and 10-minute ride will take about as long. If you use Metrolink, your ticket will cover any Orange County buses you ride.
Long Beach Airport
This is one of the more difficult airports to get to- not because the route is complicated, but because it is long. If you're flying back into LGB, be sure to be able to leave the airport before 16:00 on a weekday, and slightly earlier on a weekend. Otherwise, you may find yourself stranded. If a friend can pick you up in San Bernardino, you can be slightly more flexible with your return trip.
Ride Metrolink to Los Angeles Union Station. Take the Red Line to 7th/Metro Centre, then catch the Blue Line to Transit Mall station. Walk across the street to the north side and catch Long Beach Transit 111 to the airport. (Do not catch #112- they may have similar routes, but 112 does not stop at the airport.) Note that your Metrolink pass will cover your transit all the way to the airport, as of writing.
On weekends: Even if Google Transit says you're stranded, keep in mind the Amtrak Southwest Chief out of Union Station at 18:45 daily. (On weekdays, you'll probably want the quicker Metrolink #412, leaving at 18:35 5 days a week. They are the same price on weekdays, though, so if you want to experience a glimpse of what a long-distance Amtrak train looks like, or want to catch a quick dinner on board, feel free to grab the Amtrak. Remember to reserve in advance, either at amtrak.com or by calling 1-800-USA-RAIL. They'll have your tickets waiting at the station.)