Check out the list of titles in this British Airways registration form. It is too funny.
They serve people from many regions and cultures with different languages (Herr, Fraulein, Monsieur, Sheikh). There are special needs, such as serving Muslims on pilgrimage (Alhaji).
England is a class-conscious society, so they probably had customers wanting to register with their social and military titles. I can just see the secretary for some elderly Baron or Viscountess dressing down some poor BA functionary for not listing the correct title. I can see some web programmer throwing their hands up in despair, getting a book of titles, and including every last one.
Besides, the Pope and the Dalai Lama do fly fairly frequently with retinues. The field for “His Holiness” has probably been used.