There are many different rapid tests. Some are reliable and some are unreliable.
For the ones that are reliable (like Abbott's test), they are highly accurate at determining whether someone is currently infectious. So you could have been infected but not capable of transmitting to others yet. These tests would be highly useful for onsite testing, such as if airlines required a rapid test right at the airport.
For the ones that are reliable (like Abbott's test), they are highly accurate at determining whether someone is currently infectious. So you could have been infected but not capable of transmitting to others yet. These tests would be highly useful for onsite testing, such as if airlines required a rapid test right at the airport.