There is a premium now on establishing air corridors for key routes and then working to expand them. This includes uniform testing requirements on both ends as well as a uniform policy on quarantine, testing out of quarantine and partial test out. That should be a short collaborative process where the perfect is the enemy of the good. I would support perfection if it meant elimination of all risk. But, nothing does that. Thus, a good and efficient system now is better than something 1% better 30 days from now.

LON-NYC has long been the world's most profitable route and that requires only 2 governments to agree. Both will now requires pre-departure testing and that brings it down to whether a negative test should still result in any form of quarantine and, if it does, whether it needs to be any more than a few days to permit a second test. Uniformity as to types of acceptable test, form of the report, how it is submitted, whether it applies to transit/connections (and of what form and duration), and exemptions (which should be few), ought to be accomplished in short order. Both the UK & US need the commerce and it is possible to reduce risk.