Originally Posted by
endoman
I can vouch for the lack of logic! Currently pricing up a trip to BOM from LHR and if I pay and then upgrade with miles it's cheaper to pay WT+ and upgrade to J, than it is to pay for WT and upgrade to WT+. same number of miles for each needed. Bonkers but for 100 quid less I can travel in Club each way.
That is because you can only MFU from the the most expensive WT buckets, but can MFU from the cheapest WT+ buckets. This is very well documented. Have a read of:
http://www.flyertalk.com/forum/showthread.php?t=721790
and welcome to FT and the BA Board.