If you need it just for the flight, you'll get a blanket onboard. At least, I have 100% of international flights on AA. I have a "regular" dreamsack which is about 5X3 and tube shaped. It would add considerable warmth on a flight.

I purchased a self-inflating cushion, a fleece travel blanket, neck pillow, an eye mask, and earplugs. I'd definitely take all that on a 12-15 hour trip, but not worth the weight and hassle for a 6 or 7 hour trip (except the earplugs--don't leave home without 'em). I was really glad for the cushion on the ORD-PVG full coach flight.