Which route are you flying?

If you’re starting from a BA outstation (which likely doesn’t even have BA employees working there), then I definitely would NOT leave this for the airport. I had a rather poor experience where the IT systems were not working, but considering I had all the required vaccinations and tests, thought at the time that it would just be a matter of sorting at the airport. Airport staff at BA Club check-in counters were less than useless, and told me point blank, even as I showed them all the documents required to travel between these two countries, that if I couldn’t get BA’s system to work, they couldn’t check me in I couldn’t fly, and not to get upset with them, because they don’t work for BA and no one at the airport did either!

Sometimes the boxes you tick on the form can make a difference in what’s accepted and what’s not… I kept amending some of the minor choices (which countries I had been inside in the last 14 days, etc.) and eventually the form worked out. But this was at the airport, and I really thought I was not going to be able to check in for my flight. I was in Club and had two local friends (not flying, but they had driven me to the airport) also helping me. Only just barely made it.

Many of the IT systems that have been put in place around COVID frankly seem like they have been coded by summer interns who are back in school now, and were never tested to begin with. Total shambles, but either you’ll need to ring up to see what you can do (even that doesn’t have a guaranteed outcome), or just hammer away at the system until it accepts your data.