Regarding posts #694-#698 above I thought it might be worth highlighting an aspect of this as it's easily missed.
The CDC website mentions this:
People who have recovered from COVID-19 can continue to test positive for up to 3 months after their infection. CDC does not recommend retesting within 3 months after a person with COVID-19 first developed symptoms of COVID-19 (or the date their sample was taken for their first positive viral diagnostic test if their infection was asymptomatic).
This means that if you have tested positive in the 3 months before travel you absolutely should use the 'recovered' exemption from pre-flight testing, even if it would be easier/cheaper just to do the test. The reason is of course that you might get a 'false' positive on the pre-flight.
I think there is a case for testing earlier even if you aren't aware of having had covid. The UK has just dropped to having 'only' about 1 in 35 of the population being infected from a couple of months where it was about 1 in 20, so an awful lot of people have probably had it without knowing - the LFTs are 80% reliable at best, so aren't a good indication of negativeness.
It's obviously more cost and effort but one way to reduce the risk of a pre-flight fail would be to get a PCR test 2-3 weeks before flying. (CDC:-
Do not travel until a full 10 days after your symptoms started or the date your positive test was taken if you had no symptoms.)
If the test is negative then (unless you catch it in the next couple of weeks) it's likely your pre-flight test will be OK.
If the test is positive you can use it to get the exemption and you're bomb-proof to fly