from Lisbon to CDG to Atlanta

Uploading docs for early verification depends on the airline, and the apps/systems are different for different airlines. It should be on your airline’s website, or in an email form them.

But the pre-verification isn’t an absolute necessity. You can just show up at the checking counter with everything. (At 4am!)

Thank you very much.

I have some time the afternoon prior to my flight. I might go to the airport to "check in" and then come back in the morning with the knowledge that everything is a "go", at which point I would check bags.

Do you think they would permit that, or do you think they would say "Come back 3 hours prior to your flight?"

That's a tough call—I don't think I'd bother going the day before.

Really- Look at the airlines' sites—the information is there somewhere.

I am about to fly BER-AMS-ATL tomorrow. KLM verified my documents but still wouldn't let me check in online for the first leg of my flight (I was able to check in for the second leg). I decided not to waste any more of my last day trying, since I am checking a bag anyway, and will check in then. I would definitely not make a special trip to the airport to check in. If you have your negative test and your vaccine card, you'll be fine.
You will at some point have to fill out the attestation form required by the US. When I tried to fill it in online, it said that flights originating in AMS or CDG had to have a paper copy of the attestation and you could fill one out at the gate. Why they want a paper copy in this day and age, I can't imagine, but whatever.
PS - you have a calendar day, not 24 hours, to do your Covid test. I did the Binax now test, which was easy and I had results in my email before the test proctor even exited the call.

Thanks so much. I definitely feel more comfortable with the process. Delta's "fly ready" process was suppose to make this all easy. Based on your itinerary they would have you answer questions and upload documents and Voila! - you would be all set before you reached the airport. But as far as I can tell Delta could never could get the program to work and now it isn't even on their website (it actually doesn't seem as if it would be that difficult to create - it is a basic database, right?).

One another matter - I've now spent a week here in Coimbra working with some amazing Portuguese people, and the University and city are awesome. Since arrival I felt I was in some sort of movie (a good one). If I get stuck here because of a paperwork deficiency, maybe that is OK. :)

Safe travels to you all.

I have had mixed luck with Delta FlyReady. I went to London a few weeks ago and it worked perfectly going and coming. This trip I could not get it to work at all.
Pack your patience and good humor, allow yourself plenty of time, and all will be well. Enjoy your trip!

We just returned from Porto (RS Heart of Portugal tour), through AMS to Detroit, on Delta/KLM. Could not check-in online for anything. Could not make FlyReady work. Our flight was Wed April 6 at 5 am out of Porto (yes, ouch), we arrived by 2:30 am, but could have waited - no agents on duty until 2:45 am. They did check our test results, and passports of course, but no other forms needed. We had BinaxNow proctored test kits with us, so simply did them in our hotel room around 3 pm Wed. Had the results emailed and in the company's Navica app within 20-25 minutes. Others in our tour group used the local testing sites and had results emailed within 30-40 minutes I think. No paper needed, the emails and other digital results are fine. In AMS, nothing special was required other than a paper attestation form available at the gate (and which just got tossed into a luggage cart with no review). Passports checked of course, but they did not check test results (since they had been checked and noted in Porto I would guess). In Detroit, nothing was required other than passports. This was all on Delta/KLM. Other airlines seem to have other requirements, because why be consistent? Some travelers have mentioned a 5 page PDF that you must download, fill out, and then upload...