YouGov asked Americans about 30 things a passenger might do in the air. Phone calls came out as one of only four where the acceptable and unacceptable camps are effectively the same size: 37% against 43%. That is unusual for cabin noise. Most noise questions have a settled answer: watching a film without headphones is unacceptable to 81%, getting drunk to 82%, letting children play in the aisle to 86%. Volume, in other words, is normally an easy call. A phone call is not. YouGov grouped it with three other behaviours that divide Americans almost evenly: bringing a small dog aboard, unbuckling the seatbelt when the sign is still lit, and leaving the overhead light on. What those four have in common is that no inherited rule covers them. The behaviours that unite Americans are the ones where a rule already exists and everybody learned it young; the ones that split them are the ones where nobody ever wrote the rule down.