other European languages like French, German, Spanish, etc., where the traditional married title (madam, Frau, etc) has become the title for adult women
the word Frau is primarily the word for woman though - not the traditional married title. (not sure about French & Spanish but i expect the same).
It has been this way here for years and frankly it is nobody's business but mine if i'm married or not unless i want to share that. I order stamps from the Royal Mail and i love that i can use Mx. They have no idea what i am. Man, woman, alien... I pick that one whenever i can.
For airlines, thinking back to the days of boarding cards I'm pretty sure mine have only ever shown F and the DCs back in the day had CHD. So i think it's just a local cultural thing. But if this is the 3rd time they need to get their backsides into gear.