If you search for flights out of Philly and select 'surrounding airports' you'll sometimes get a cheap fare that starts at ZFV. Well ZFV is the 30th Street Station in Philly. Your first leg of the flight is on an Amtrak train for an hour from Philly to Newark, then the airtram to the airport proper.
My last flight to Shenyang was ZFV-EWR-PEK and PEK-EWR-ZFV back. It saved about $200 off the cost of flying directly out of EWR (same flight as confirmed via United and Google flights).
So, was it worth it? Well, no.
First, parking at the 30th street station is about $30 a day. So for a week of parking you're already $210 in. Good bye 'savings'. So what I did was I parked at normal long term airport parking spot (Colonial Parking) at PHL for $6/day. Then I took their free shuttle to Terminal A and paid $7 for the dedicated airport line that runs straight to the 30th street station. The only downside is that you need to add 1 hour to your trip. That's not including the 3 hour drive to the airport. So right now I'm 4 hours in, and paid ($6x7=$42 + $7x2=$14) $56 for parking and trains to and from ZVF) So far I saved $150 vs parking in Philly.
The train was to leave at 8am (ZFV-EWR). The trip is an hour long. But my flight was not until 11am.
Now you get to the BIGGEST ISSUE. The codeshare tickets SIMPLY DO NO WORK. You're supposed to be able to get the train ticket from an Amtrak automated kiosk at the 30th street station. LOL NO. You're never given the required Amtrak reservation code from American OR Amtrak. I had to wait until the attendant opened and get the ticket from a person. And even then they asked me a ton of questions about what exactly I needed. After reading a lot of other posts, this is common. The United and Amtrak computers SIMPLY DO NOT TALK TO EACH OTHER. This happens again on my return trip.
So I get on the train, find my reserved seat and wait for the conductor. Now the NEXT HUGE ISSUE occurs. Since the ZVF-EWR is considered a 'leg' of your flight, YOU MUST GET THE CONDUCTOR TO SCAN YOUR TICKET, otherwise you miss your 'flight' and there is a very real risk that your entire trip gets cancelled. There are ways around this (book two one way tickets vs one round trip) but since I was on an international flight 2 one way tickets was not a real option. So I nervously waited for the conductor and asked him if he could verify that the scan was accepted. Again, 99% of the people will have ZERO clue about this train-plane thing and will simply not have any answers for you. Get used to that feeling. Also, the Amtrak app is useless, and the United app never even shows any train related boarding information. The train is nice and comfy, free wifi and quiet. Evidently this ticket from 30th street to EWR is over $150... but for this codeshare ride it was not. Once you get to Newark airport, you get off the train and ride the airtrain for free (normally its like $5) to the airport and then magically all the United things start to work/make sense.
Coming back from PEK-EWR was uneventful. So now I have to catch a train back to Philly. I landed at 4:00pm and my train was scheduled for 8:00pm.. so another 4 hours to burn.. which were actually needed. So I take the airtain to the end (the NJ Transit station) and the attendant told me where the Amtrak kiosk was. So now I'm back to 'what the fuck number do I use???' United's app never shows any Amtrak boarding pass, and the flight number for the 'flight' (aka train) to ZFV/30th street didn't work. I tried every combination of my name and gave up. I called the Amtrak 'help' number only to realize that the 800 number has no idea about codeshares and simply directed me back to United.
So back on the airtram and to the United customer service desk. I explained what happened and showed them my tickets from when I left, and my United record number. An hour later (actually more like 2 hours because of the time to call Amtrak and talk to them) I was given a hand written reservation number and was told to try that at the kiosk. I was also told that if the kiosk didn't give me a boarding pass, just have the conductor type in the reservation and that 'should work'. So back on the airtain and back to the Amtrak kiosk and you guessed it, nothing worked. At this time its close to 8pm and I go to the NJT attendant and show them what I have but nothing that will let me past the turnstile. The lady said 'I don't work for Amtrak but I'll let you through, but you cannot get out without a ticket'. Not sure what that meant but I just said thanks and she let me through. I find the right track and find out that train numbers are worthless. Nothing on the monitor was matching the train numbers that were showing up, so I would have to ask every conductor for every train if they were the train to the 30th Street Station. Well, another guy helped me out and showed me the monitor and how to read it.. and that the train I needed was 30+ minutes late.. so about 9pm.
Well 9pm-ish rolls around and the train arrives. I get on and repeat the process at the 30th street station: buy local train train ticket, get to PHL airport, call the parking lot for a pickup and get to my car.
So compared to flying direct from EWR was the $200 less for the ticket worth it? NO. It added almost 8 hours to my trip (waiting for trains, train time, needing to arrive early to park etc).
The cost of parking is nearly the same at airport long term parking, but the extra time and expense of the train to/from PHL to ZFV, the complete uselessness of any ticking information from Amtrak or United really started the tip on sour note. I mean on the return trip United never even 'bought' the ticket from Amtrak from EWR-ZVF.
My tips if you do this cluster f*ck:
Build in plenty of extra time. Ticket issues and trains that run at widely spaced intervals (the train from PHL to ZFV runs every 30 minutes). Nothing is automated and the left hand simply doesn't know that the right hand is doing.
If it was a $400+ difference, sure. But next time I'll pay the $200 and not burn 8 hours and have all the stress of being stranded because of train ticket nonsense.