LHR - BLR J seats on BA are a bargain in Aadvantage miles (60K RT), if you can make the odd flight timings work for you. You would probably want to take the late JFK - LHR flight on either BA or AA, and would also have to make arrangements for a very early check-in to your BLR hotel. One serious advantage to the BA flight (besides the great upstairs J cabin) is that you won't encounter any local BLR road traffic, either arriving or departing.