B-Flex (the Premium Eco) can be a good deal but be very careful never to take a codeshare flight. I did it with a flight to Lisbon using TAP and I must say that the website of Brussels Airlines is very misleading you would need a magnifier to note that this is a codeshare flight. As a consequence you are denied any of the B-Flex perks: staff at Brussels Airlines check-in does not even recognize you and send you to make the full queue at TAP check-in. You receive no fast track at the security. You receive no preferred seating no snack not even a drink. You are basically a simple economy passenger stupid enough to have paid a B-Flex fee instead of the cheapest economy fare. I got the Brussels Airlines flight on my return and then had nothing to complain I received all the perks and was quite happy of the flight. In my view the Brussels Airlines website is totally dishonest as even their confirmation told me about those perks I was not going to receive on the TAP flight.