What an excellent euphemism for BA's IT development team having not got the job complete.
Due to the changes we have made to ba.com to stop charging APD for young adults, you are currently unable to make online bookings for young adults to travel alone.
Our colleagues over on Flyertalk have got a 28 page (and building) thread, including contributions and indeed some proposed fixes by a number of notable IT pros, on errors and omissions on the BA website, which you will see is read by the BA IT management !
Issues, bugs and glitches on ba.com website [Please keep thread clutter-free!] - FlyerTalk Forums