From Lucerne to Milan

A few questions-
Are you taking the Bernini Express route into Italy? That is one of the most beautiful routes anywhere.
A sale on the various STP begins April 15.
There is a wealth of info already posted here under the Switzerland section, so review the last several threads for more detailed info.
Safe travels!

The fast way from Luzern to Milan uses the Gotthard Base Tunnel, which is 35 miles long completely under the Alps, ie, not too scenic. There are a couple of direct trains each day to Milan. At other times with a single connection at either Arth-Goldau or Lugano.

For a slower, more scenic route, you can take the Treno Gottardo, which goes mostly over the mountains with a shorter tunnel. You have to change trains at Bellinzona for Milan. This route takes about an hour longer than the fast route (4 1/2 hours).

Finally, there is the Gotthard Panorama Express, which uses the scenic route, but starts with a boat ride from Luzern to Fluelen, where you change to the train. This train is all 1st class, so with a 2nd class Swiss Travel Pass, you have to pay a supplement for the upgrade plus a seat reservation fee. That train ends in Lugano, so you then change to a train to Milan there. With the boat ride, this is an all-day affair.

Yes, with a Swiss Travel Pass you get credit for the Swiss portion and only pay for the section from Chiasso to Milan.

If you are not going the Bernina Express route mentioned above than you need to buy a separate ticket from Lugano to Milan. Your Swiss Travel Pass is good up to the last town before you cross any bordering countries.

The train between Luzern and Milano Centrale is not necessarily scenic; most trains use the deep Gotthard Basistunnel under the Alps. You have to carefully select a train that does not use that tunnel to have the scenic route over the Alps( there is still a tunnel at the top, but it is very short).

Your choices for staying on the scenic route between Luzern and Milano Centrale are:

The Gotthard Panorama Express boat plus train combo between Luzern and Lugano:

https://www.sbb.ch/en/leisure-holidays/trains-trips/rail-travel-specialtrains/panorama-trips/gotthard-panorama-express.html

The Treno Gottardo between Luzern and Locarno:

https://www.myswitzerland.com/en-us/experiences/treno-gottardo/

Or a combination of regional trains that stop in Göschenen ( this may involve a train change and can be harder to figure out than one of the other two trains).

The Bernina Pass train that Pat asks about is a detour to the east and would take longer.

Your Swiss travel pass will cover you for all of the journey within Switzerland. Pick one and people can help you figure out what tickets you need to go from Lugano or Locarno the rest of the way to Milan.

Edit: I was posting at the same time as Sam so duplicated his information. But maybe you will find the links useful.

Thank you all for the info. That really covers my questions.