We are trying to buy our airplane tickets to Milan but I see that there are three airports listed! Does it really matter which one I use or is there a best option?
Also, we’re flying out of Rome. I’m finding the same thing 3 airport to choose from!
Seattle to Milan,
Rome to Seattle
Malpensa is the international airport, Rome’s is Leonardo da Vinci–Fiumicino.
Any particular airline or are you searching 'everything' ( e.g., expedia or similar)?
When you do your search use SEA - MXP, which is Milan Malpensa, however select the "include nearby airports" option (there is usually a box saying so in all search engines) that way you'd be able to see the options for Milan Linate (LIN) as well. Many European airlines fly also (or only) to Milan Linate from their respective hubs, therefore you want to make sure you include that option, otherwise you won't be able to see those options arriving at LIN. The other Milan Bergamo (BGY) airport is not used by traditional airlines, only low cost European airlines (mostly Ryanair and WizzAir), therefore there would be no options for a flight from Seattle with any traditional airline.
For Rome just use Fiumicino (FCO). Rome Ciampino (CIA) is used only by low cost European airlines, therefore it would be of little use to you going to North America with a traditional airline.
Therefore for your multi-city trip do the following in the search engine you use (Kayak, Google Flights, etc.):
Going: SEA - MXP (but also select the include nearby airports option by checking on the box saying so)
Returning: FCO - SEA
Linate is the one "in town"
Malpensa and Bergamo if those are the other two being referenced are 45min to an hour out of town depending on what side of town you are going to.
If the remote ones are cheaper the transfer might be a bit more. I would go with the best deal that works with your budget and schedule.