KEEP BRITAIN FREE
Many airlines demand doctor's note (need to check with individual airline).
KLM even stipulates specification for the mask and how it has to fit, other airlines stipulate that it has to be made specifically for this purpose (i.e. no bandanas).
I'm a bit worried that if one refuses to wear it then they would use the failure to follow cabin crew instructions or endangerment to air traffic excuse which could be a serious offence in most countries ( I have read reports of this being used in the Netherlands and USA).
They all give exemptions for eating and drinking so a large bag of small crisps is the way to go 😁