Definitely take a sling! We've travelled several times with DD (she's been on 6 flights already!) and our slings have been our saviors. We have an Ergo and a Bubba Moe. The Ergo is a great all rounder and especially good while at the airport. I usually put DD in her Bubba Moe to sleep on the flight (when we haven't had access to a bassinet onboard) as she can lay in the cradle position. She did sleep well on one flight in the Ergo though too.

As one of the other girls said, they can't be in the sling for take off or landing but we've gotten away with it twice now. The two hosties that let us do it just helped me to thread the infant seatbelt around DD while she was in the sling. It was great as both times she was asleep so we didn't have to wake her, yay! Keep that in mind, you might just get a nice hostie.

I've taken DD to the loo many times with me while she's been in the sling and it works well. You need to keep the loose straps out of your way (lol) and wiping is a little more difficult but it saves getting them out of the sling and trying to keep them in one place if they're mobile!!

Your arms will tire easily so the sling really helps with that too. I wouldn't travel without mine