Ubiquiti Airtime Fairness
Ubiquiti Airtime Fairness takes airtime and splits it up between wireless clients instead of giving clients the same amount of data transfer. This makes the connection faster for someone connecting at a high rate and good signal level but it will also slow down a connection that connects at slow rate and bad signal levels.
ATF (Air time fairness) uses more resources on the access point when it enabld so it also limits the number of clients that connect to the access point. For example AC pro access points should not have more than 20 clients on them with ATF enabled.
To be able to see the Airtime Fairness properties on the device, make sure you enable Advanced Features first under Settings -> Site -> Services.
Airtime fairness compared to packet fairness. You can see below that if you connect at a higher rate of speed then you can transmit more packets in the same amount of time