Downsides to flying into Pisa from U.S.?

The first reason is that there aren't (anymore?) any direct flights between Pisa and the US. Delta used to have one - don't think so anymore. But one can generally fly into/out of Milan, Venice, or Rome from the US.

Otherwise, I'm not sure there's any reason not to fly into/out of Pisa if you connecting works better (or just as well) to get to/from Italy anyway. Depending how I fly, I can get direct flights between my home city and London, Amsterdam, and Frankfurt; if I could get a connecting flight to/from Pisa and that put me close to the start or end point of my trip, I'd certainly do it. Last year, I got a direct flight to Venice, and I was headed to Slovenia anyway. A few years ago, I was departing Italy from the Cinque Terre, and Pisa would have worked except I got a ticket via Milan instead with a stop-over in Amsterdam (then a direct flight home the next day).

If it works for you, do it. Not sure Heathrow would be my first choice for connecting in Europe, though.

I flew into Pisa from the US (stop in Oslo, Norway) and it was a great BUT the reason is exactly as Andrew mentions.
Pisa comparatively is a tiny airport and has no flights from the US that land there so of course it would not be talked as often as the big 3 you mention which all have flights from the US that land there.

Nothing undesirable about flying into Pisa. Smaller airports are typically much easier/less stressful for the traveler.

I see that you are also in NC, as I am. We use Raleigh-Durham airport and there aren't many choices in direct flights to Europe. We flew to Pisa for our October trip, through Heathrow. Partly because we were using frequent flyer miles and also because we were starting our trip in Vernazza so not a long train trip after arriving. Really didn't want more than one connection if we could manage it and it worked out fine although the flight out of Heathrow was delayed a bit.

I have not flown into Pisa, but I have flown out twice. There is nothing wrong with the airport. It just happened to be the most convenient for me at the time.

My $0.02

Pisa is not a 'destination' in the way Rome, Venice etc are.

I suspect most folks stop for a few hours in Pisa to see the tower on their way to somewhere else. Making it one's 'destination' airport probably does not make sense for most travelers.

Of course, if you are doing a classic Venice-Florence-Rome itinerary, then Pisa makes no sense as an arrival or departure airport.

But many people do northern Italy itineraries that may start or end near Pisa, which makes a practical start or end point for the Italian Riviera. it's barely two hours between the Pisa airport and the Cinque Terre by train. We see fairly regular itineraries posted here where people fly into Milan to get to the riviera - Pisa would be a lot faster for them. (So would Genoa, but Pisa may have more flight options.)

Also, just because many tourists don't realize there's more to Pisa than the Tower doesn't mean there isn't more. It's certainly not Rome, Venice, or Florence, but it's not a wasted night to stay one in Pisa before a flight home - with a ten minute "people mover" train rride from Pisa Centrale to the airport, it's a bit less stressful than flying out of Milan, Rome, or Venice, which are much further from their biggest airports. Some would prefer Lucca over Pisa - still not far from the Pisa airport.

No downsides or upsides. Whichever airport works for your plans is good.
However it is not true that a lot of flights to Pisa go through London Heathrow (LHR)
There is actually only one flight a day (at around midday) from LHR to PSA and back. It is operated by British Airways. A couple days a week there is also a second such flight later in the evening.
Most flights operating from Pisa are with RyanAir and other low cost European airlines.
Of the traditional Airlines only the following connections are available:
Alitalia (to Rome)
Lufthansa (to Munich)
British (1 to LHR, but most to Gatwick)
Turkish (to IST)

Thanks for the responses! The itinerary I'm mulling over would be Lucca, Ravenna, Siena, and possibly Orvieto, which is why I'm interested in the Pisa airport.

Then look also into Bologna (BLQ), which is near Ravenna,or Florence (FLR)

Lucca, Ravenna, Siena, Orvieto - sounds like a great trip. We have loved all of those towns. As for Pisa airport, all I know is that when my son spent a year in Florence as a student, the Pisa airport is what he preferred to use.

We flew BA and AA due to points so we had to go thru Heathrow so the advantage of the direct flight was off the table. We were going to Cinque Terre and Lucca so Pisa was a perfect fit. Smaller airport, close to CT and Lucca, I saw nothing wrong with the Pisa connection. If you visit Lucca I encourage you to hire a private walking guide if possible. We used a lady Rick recommends and she was awesome. We hired Wanda Martinelli of www.Luccatours.com and she was fantastic. We did a half day walking tour on our first day in Lucca and she set us up for great touring for the next couple of days. She gave information we would never have seen or have known about without our walking tour with Wanda. Here is her email from the website. [email protected]

Both times I used Pisa airport was because I stayed in Lucca. Quick, easy trip to the airport.

Thanks for further recommendations, especially for the walking tour of Lucca. Lucca is the only one I've visited before (briefly), and I'd love to learn more about it. An 'extra' I'd like to do in Ravenna would be a one-day mosaics-making class, and when in Siena, I'd like to hike off into the countryside. Also, when traveling among towns, whenever the train or bus stops in Firenze, I'd like to get off, check my luggage, and go see something I missed previously (San Miniato al Monte, Santa Croce, etc.).