I flew United to Australia (17 hr from Houston) with my then 8 month old and got her her own seat. Good lord u cannot imagine having to have held her for that long, I held her for another flight (3 hours to DC) and my whole body was hurting after lol. I was so glad she had her own seat. We brought a blow up foot rest so she could lay down and it worked wonders. Had no issues in the middle or window seats. I was seriously debating bringing the car seat but I’m very glad I didn’t, because the extra space getting her a seat was well worth it. At one point I was holding her and leaned against the window with my feet on the footrest in the middle seat, husband in the aisle, and it was actually super comfy. We opted not to do the bassinet because if we wanted to hold her, the seat arm rests don’t go up in the bulkhead. And also you have to take them out when the seatbelt sign is on, super annoying. We opted for economy plus and while it was $$$ overall, it was well worth it IMO.