Im flying BA from LHR to JFK tomorrow. Ba ask you to download the Verifly app which was simple and vidated international vax certificate instantly (QRs are useful).
But then I also had to redo the attestation in MMB at BA.com, that upload didn't validate immediately took BA 5hrs to manually check but once confirmed (also needed to make sure APIS was up to date, note BA ask for details that QF APIS doesnt) I could check in online.
There was a warning g re needing an ESTA and a passport but no request for the details.
Will see what happens when I collect boarding pass and do bag drop tomorrow.
When I last did this flight in 2019 was not asked to show ESTA as it should automatically be linked to passport.
** edited to add, arrived at airport used kiosk to scan passport and print boarding pass, then went to automated bag drop (no option to check in or do bag drop with a persom at north end of lhr T5) and straight though express path security. At no stage did anyone ask to see my vax cert or ESTA.
*** edited agin to say entered via JFK about 40 mins ago, was not asked to show ESTA or vax proof. 5 questions only: purpose of trip?,where are you staying? How long are you staying,? Do you have anything to declar? How much cash do you have?