Oh boy, I don't envy you this one! I've nursed easily distracted babies in public before, and it can really be a challenge, never on a plane, but darn near everywhere else you can think of, including a football game. (Okay, taking a 9 month old to a Bomber game wasn't the best choice I've ever made, but it was the Labour Day Classic and they were supposed to win. It was a long time ago. I realize they don't, in general, win anymore. And that only made sense to the Canadians. Sorry.)
I'd put one of his really snuggly blankets where you nurse him most often for a few days before you leave, so that it will really smell of the place he associates with good sweet nummies and quiet time with Mummy. (I'd put it in my bed, 'cause we co-sleep, and that's where my little guy does most of his nursing now, but wherever you nurse the most will do it.) Stick it in your carry-on and when you want to nurse, just snuggle him in it, the smell of home and familiar feel of the blanket really cuts down on their agitation.
None of my kids would ever put up with having a blanket over their heads after about 3 months either, and it will probably just tick him off so I wouldn't bother. Nursing as much as you do, you're really good at it by now and unless somebody is actually staring at you, they probably won't even realize what you're up to. I've usually used cradle hold and spent most of the time looking in their eyes and talking or singing softly too them so they don't get distracted by any noises or lights they arn't used to. (Do you know that magic bubble you sometimes feel like the two of you are in when a feed is going beautifully and everything is just perfect? Try to make that on purpose.)
I was just IMed by one of my girlfriends who has nursed on a plane, and she said that she basically did the stuff I mentioned above and the white noise and motion of the plane really helped her son relax. She also said to remind you to try to get him latched on for take-off and landing so his little ears wouldn't hurt.
I hope you have a great time and your little guy turns out to still be a wonderfull flyer.