I actually just flew United with my 80lb dog from BsAs to Chicago (via Houston) a few months ago.
United is the strictest airline about kennel size and other requirements... honestly for anyone flying with a dog that doesn't touch the top of a size 500 kennel while standing I would recommend going with another airline. However, they are the only ones that will ship kennels larger than 500 - which you can definitely find in Argentina. I spent months waiting for a good deal on a used one, but if you don't mind spending a bit more something like this should work:
123x82x90cm:
http://articulo.merc...-82-x-90-cm-_JM
If you're shipping the dog cargo with United anyway then switching to a slightly larger kennel doesn't cost you very much more. Even though they will quote you a price in dollars you CAN pay the cargo company in pesos (based on the t/c reuters exchange rate, way lower than blue) so you can save a ton doing that.
I would contact DAF asap... ideally you'd confirm everything with them before buying a plane ticket, but at a month out you still have plenty of time to arrange everything. United provided me with contact info for the two cargo companies listed below, in my case DAF was more helpful and gave a slightly lower quote than the other.
Contact name: Rodolfo Galiardi
CRISTOFERSEN INTERNACIONAL S.A.
Tel: (+54.11) 4314-2336
[email protected]
www.cristofersen.com.ar
*************************************************************************
Contact name: Luis A. Gonzalez
Daf Cargo S.R.L.
Ph: (5411) 4295-6866
Cel: 155-302-8486
Cel intl: (54911)3834-7460
[email protected]
www.dafcargo.com
However even they weren't very informed about which connecting flights my dog would be allowed on - Chicago was the closest I could get to my destination despite them initially saying they'd fly him to other cities! So check if any United planes going to Atlanta would take him, maybe he could travel on one right before or after yours if your plane is too small. Large kennels are not allowed on Express flights or Boeing 737. I took a quick look at Atlanta flights and one like #
UA1226 which is an
Airbus A319 should work.
Your vet should know all about the forms you need (though the fact that he or she wasn't aware you can buy larger kennels isn't a great sign)... try to get them as early as allowed because sometimes there are delays. Check for holidays around your departure date - could mean trouble getting the forms (SENASA closes) or you could be charged almost double if you try to fly on a holiday or weekend.
Oh and I found attachable food dishes and water bottles (required) from Centropet downtown, small pet stores often don't carry them.
Hope this is helpful!