Como to Lauterbrunnen to Lucerne - Train help!

"even though I looked months early, I was never able to find EC52 tickets from Milan to Spiez"

That is your problem. You are trying far to early. What is your actual travel date? Currently there are lots of engineering works on that line, an for that reason trains only open for booking a week or two before the travel date.

If possible swap Luzern and Lauterbrunnen, or spend all your time in Luzern. With only 2 nights you do not have a lot of time to actually do things, especially if the weather is bad.

Regarding passes: If you decide to do the Varenna - Luzern - Interlaken route get yourself a day saver pass for that day. (on www.sbb.ch) and then just buy Varenna - Chiasso at the station. This route is the most interesting one. Especially if you go over the old Gotthard line.
https://www.sbb.ch/en/travelcards-and-tickets/tickets-for-switzerland/day-pass/saver-day-pass.html
Saver Day Pass is valid on all public transit in Switzerland, so you are free to take any route.

You can make the day pass cheaper (as well as any other transportation) by getting the Half Fare Card. That is especially interesting if you are a family with children.
https://www.sbb.ch/en/leisure-holidays/inspiration/international-guests/swiss-halffare-card.html

Varenna to Lauterbrunnen is going to be a long day on trains no matter what route you take., . If you can change the order of travel as WengenK suggests, putting Luzern before Lauterbrunnen, you will see routes from Varenna to Luzern that are only 4 hours 6 minutes.

I appreciate the feedback!! The reason we did it this way instead of Luzern first was to be closer to the airport upon departure! Lauterbrunnen is really the reason we wanted to go to Switzerland in the first place and then we figured Luzern was on the way back so we decided to do both!

I had heard that some train tickets sell out 6 months in advance, which is why I was concerned that they may already be gone. I got a notification from a third party site that they were available and when I went to book, they were unavailable, so I thought I missed out. Good to know they may not be available yet!

You all are truly helpful for us that live across the world and have very different travel experience than that of Europe. Thanks again! :)

I wish I had a nickel for every poster who plans a trip from Varenna to the Berner Oberland. It is a long slog.

The Half Fare Card at 120 CHF plus a 3-day Berner Oberland Pass at 150 CHF (with the Half Fare Card) might make sense, but it makes it even longer day. It is Valid from Domodossola to Lauterbrunnen, but you must take the slow way from Brig to Spiez by going via Kandersteg. It is more scenic than the fast way using the Loetschberg Base Tunnel (which is not valid with the B.O. Pass). That will be good in Lauterbrunnen, especially if you go to Klein Scheidegg instead of Schilthorn. Then the third day it will get you to Luzern.

What time does your flight depart Zurich?

Yes, Luzern is closer to the Zurich airport, but the journey from Lauterbrunnen to the Zurich airport is only 2 hours 42 minutes. There is an 8:32 departure from Lauterbrunnen with a single change at Interlaken Ost that will have you at the Zurich airport, inside the terminal, at 11:14 am.

With an afternoon departure from Zurich, you could still put Luzern first to ease your journey to Switzerland. Spend one night there and then the remaining 3 in Lauterbrunnen since that is your main goal.

Or, if your flight is in the morning, make it one night Luzern, two in Lauterbrunnen, and one in Bern ( travel there in early evening to have a full day around Lauterbrunnen).

Ok I need help again!

Same trip, but now it seems all my alternative options are dwindling. There is construction in both directions. Can I even get from Milan to Interlaken at this point? Should I just fly from Milan to Zurich and get a train from there? Is that ridiculous? Getting very concerned that we will have to cancel the Lauterbrunnen part and that is the highlight of why we are going. For specifics - the 15th of Sept is when we are heading there. (The Lucerne stay is non-refundable at this point, Lauterbrunnen and Varenna may still have some flexibility)

Also, which website would be the most reliable for this trip on accurate timetables and available seats?

Thanks,
A panicked American

Can I even get from Milan to Interlaken at this point?

In looking at the SBB app, I see plenty of trains from milan to Interlaken on Sept. 15th. Yes, there is construction, but there will be replacement buses for that portion of the journey. You can see all this info. on SBB.

Ok, that makes sense. As long as I know that one is the accurate one I will stick to that. Thank you so much! We don't even have trains where I live so it is a little stressful. :)