@SAR
To answer your question for a tagged training scheme there were several internal candidates successful in the BAFPP during the first 2 years, and I expect more from the 3rd intake. No limit on age. Their previous roles were varied: Revenue Management, Cabin Crew, Engineering to name a few. Being an internal applicant doesn't guarantee anything, but it does help to understand the business and build company relevant experience to talk about in an interview.