Originally Posted by lhrsfo

All true but this will come into its own in countries, and between countries, where infection rates are already low. In such a case, the chance of any individual having COVID is already very low. The chances of the test providing a false negative very low. The chance of an individual contracting COVID between test and flight is extremely low. Whilst you have to add those chances together, and multiply by the number of people on the plane, you still end up with a very low chance - low enough not to concern the arrival country and low enough for other travellers to feel comfortable taking the risk.