How much time needed in Atlanta?

I think you'll have no problems unless your flight from Seattle is terribly late. ATL is big, but the train system connecting terminals is efficient and easy to figure out.

If your flight to Venice is non stop to Europe, it will leave from the international terminal and that is a separate terminal from your arrival terminal. If your flight to Venice does stop anywhere in the U.S. before going to Europe it will leave from one of the domestic terminals. In either case, you should not not have to leave the secure area to get on the out bound plane as the "plane train" serves all the terminals. But things do change all the time in Atlanta. With only a carry on you should be able to make it if the arriving flight is on time. Think I'd take a chance with ATL before JFK.

We flew out of Atlanta last year and we had plenty of time to get from our Domestic terminal (which I believe was B). The plane train is very easy to get to and use. I believe we had 2 hours but we could have gotten away with an hour layover. If you want to get something to eat I would pick something up in the domestic terminal because have more to choose from and easy just pick it up and go. If your plane is on time you should be good to go.

A second to the Carole's advice: if you need food, buy it in your arrival terminal in Atlanta (if you have time). I've found the international one distinctly lacking in options.

It is quite fast getting among the various terminals, they're all on a straight line connected by the airport train. If your flight from Seattle is on time, you shouldn't have any problem. Of course that's an IF!

Forgot to mention the food options, but Carol and Kim are spot on about them being better in the domestic terminals. Believe me, you don't want to have a Varsity chili dog just before an overseas flight.

Atlanta is my nemesis airport (I won't freak you out with the details) but it's always been coming back from Europe where the problem occurred. A few weeks ahead, use a flight tracker to see the timeliness of your SEA-ATL flight and the ATL-Venice flight and note their general gate locations - though it might not be the same for you, you can get an idea and study the ATL maps for most efficient route. Then when you check in I'd ask nicely at the gate in Seattle if they can tell you in advance what gate you'll be at in Atlanta - if not, the flight crew might be kind enough to help you out (just ask when they have a bit of down time). Also, use the facilities on the plane before you land...I find this substantially helps with focus when you're dashing off one flight to another :)

I agree with the consensus. Assuming there is no delay you should make it easily. If I have a choice where to change plane: JFK or Atlanta, Atlanta wins.

TC, did you hear my groan when I read your "Varsity Chili Dog" comment? ugh! I don't want one, and I hope no one else in the general vicinity brings one along, either - ha!

Thanks everyone for your replies! Consensus is to accept the Atlanta option vs. JFK.

Two years ago we planned to fly Delta Seattle-to-Atlanta-to-Zurich to arrive in the morning, catching 4 trains into Wengen, Switzerland. They changed our flights, and we ended up going through JFK. I'm hoping to not see JFK on this trip! : )

One nice thing about the ATL is that even though it's way too big, at least all the terminals are behind a common screening area and you don't have to re-clear security when making a domestic to international connection like you do in some airports. You just have to walk briskly from gate to plane train to next gate.

I'm not sure I would prefer Atlanta. Some years age we flew to Stuttgart on Delta's ns flight from Atlanta. It was a longer flight, I think, from Denver to Atlanta than from Denver to one of the mid-Atlantic airports, then, after we took off from Atlanta, it took an hour flying up the east coast until we went over those same mid-Atlantic airports that would have been closer to Denver. It made for a very long day. From now on I'll try to fly through Chicago.

As for changing concourses, our flight to Stuttgart went out of the same concourse that our flight from Denver came into, there was no changing concourse; we just walked down to the end of the concourse to our Europe-bound flight. Maybe it's changed since my flight, but I don't find this situation to be unusual. I've also flown out of a domestic concourse in Chicago and Detroit, but back into the international terminal on my return.

In Denver (as far as I can determine), all of the airlines with direct flights from out of the country use Concourse A. After arrival you are herded to the lower level which is connected by a secure passageway to international arrivals in the main terminal. The plane stays at the gate and loads from the upper level.