Weighing select passengers at airports would establish a more accurate number for average passenger weight so the number of seats available on flights can be adjusted accordingly. It isn't clear if the passenger would be penalized in any way, but the airline would then have to move on to a different random passenger. It also states that a passenger's weight should not be estimated if they choose not to participate in being weighed. 'An operator should ensure that any passenger weight data collected remains confidential.' Weighing passengers for balance purposes and to calculate fuel burning isn't unheard of overseas.

Source: Daily Mail May 17, 2021 15:50 UTC