We flew with lo when he was 11 weeks and looking back its alot easier then compared to now! We just took a feed for the flight change of clothes, bibs, dummy, he was good as gold and slept the whole three hours!
More or less only waking for a change and bottle. You can bf during the flight but not taking off or landing apparantly! As for the seatbelt we did the same as laurenmm and just had it loose and cradled him, have a great time!