Well, this is a little awkward. thai airways
While other airlines are encouraging larger passengers to travel in business class rather than economy in order to be more comfortable, Thai Airways have banned obese passengers and parents with young children from flying business class on its new Boeing 787-9 Dreamliners.
Thai Airways’ new airplanes include brand new Zodiac Cirrus seats for its Royal Silk business class in a more spacious 1-2-1 configuration, in which the seats convert to a fully flat bed and allow privacy and direct aisle access. New airbag system in safety belts has also been installed.
However, passengers with a waistline wider than 142.24cm (or 56 inches) will not be able to fasten the new seatbelt airbags in a way that meets safety standards. The new airbags will also make flying difficult for parents of young children, who will now be forced into cattle class if they need to travel with their kids sitting on their laps.
Normally larger passengers are issued with a safety belt extender. But the airbags must be centred over the traveller’s waist to be safe and effective. The maker says, “The airbag deploys up and away from the seated passenger, providing protection to the head, neck and torso.”
Therefore, an extender would completely reduce the protection.
[Source]