Northern Italy, Switzerland and Austria -- two weeks in May?

Hi, you will get more helpful replies if you can give us an idea of what you’re trying to plan to do while there - lower elevation hiking or sightseeing, or higher elevation skiing?

The best airline is the one that serves your area, with the least amount of stops. Also, you may want an open jaw, multi-city ticket, so that you aren't back-tracking. For instance, fly into Venice, and out of Zurich.
I think three countries is too much for two weeks. I would be really happy with spending all two weeks in Switzerland, and have done that a few times!
However, to reduce travel time, probably Switzerland and northern Italy would pair the best.
May is a little early for the higher altitudes of the Alps, as many of the lifts and trails aren't open until about mid-June. However, there's still an abundance of beautiful vistas to enjoy.
It would help knowing your interests, group size, travel experience, mode of travel, etc., before giving more specific advice.
Safe travels.

Thank you so much for your replies and input. I should have added more details, sorry about that. We are in our mid 60s, but pretty active. We have been to Europe about five times and our perfect day is setting out to walk the town we are in and stopping often to see sights and just soak up the culture. Not into nightlife, wine, crowds (if we can avoid them). We usually do about six miles a day, but our major hiking days are behind us. Would love to hike somewhere in the alps, if not too much elevation, and relatively flat. I know, that's probably not likely.

You have already convinced me to just do two countries and we chose Switzerland and Northern Italy, mainly the Lake Como area. Thanks for any advice or thoughts you have. :)

The Val Gardena area of the Dolomites (near Ortisei) has a number of opportunities for easy, relatively flat hikes where you can take a cable car lift to a higher elevation. Laurel Barton, a contributor to this forum, wrote a book with directions of easy hikes in the Dolomites. Edited to say that I had forgotten that you said May which might be too early for walks in the Dolomites. Most of the lifts don't open until mid June.

From Varenna (Lake Como) you can easily do a day trip riding the Bernina Express or the regular Bernina route train which you pick up in Tirana.

Two weeks, as you realize, is too short for all three countries. Where do you live? Swiss Air is great if you live close to its gateway.

I think where you want to go depends on your budget too.