I used Verifly 1/29 at GRU. It is clunky and cannot read negative covid test in a non english language. Since required to return to USA, this is a big problem. Luckily my lab also issued report in english 1 day later, and photo upload worked. AA agent at GRU looked at the app at check in and I did not have to produce paperwork. I hope Verifly and AA improve the process if they hope flyers will use.