Originally Posted by
GentleGiant
They can always say that they booked at the weekend when the dress comes out!
In all seriousness, these days it would probably be a brave airline to question what someone wishes to call themselves.
Indeed. Moreover the airline will change the options according to the point of sale. So on the Spanish language BA site, your only options are
Sr
Sra
Srta
Dr
Dra
Now the last one is interesting since in English the concept does not exist, at least in the honorific form. Either way we have to select an answer that suits rather than the one that is necessarily accurate.