Thx for input, but the only way I know to convert flight credit is by using it toward the purchase of another ticket, with any remaining balance getting converted to trip credit. It's not clear to me why I can't use the flight credit to purchase BE directly, which would increase the value of the remaining trip credit. From what I can read in the t&c, it seems the only requirement is that the flight credit be used to purchase another ticket in the name of the original passenger. It doesn't say anything about which fare class.