Bassinet weights vary by airline, but on ANA (the airline we usually use for long-haul) the bassinet limit is 10 kg (22 lbs) which would be enough for many 11 month olds. It was enough for ours anyway. Even if the baby is near the limit for the bassinet, it can be helpful to have some place to "store" them with some toys while you eat, fill out paperwork or whatever. Obviously a seat with a child seat is the best for this, but the bassinet can work for this purpose too.