Re: Baby Leash?
IMO, I'd just let her run around. It's hard enough to keep a kid still on the airplane. I'd let her run around while she can and get it out of her system. If you are going with your dh's parents, then there will be enough people to take turns keeping an eye on her and someone to stay with the luggage. I live in thailand and have made that trip from the US by myself with him. I've never had a problem keeping track of him and my luggage. I always let him run around at the airport and stretch his legs because he has to sit for such a long time. I'm not opposed to leashes at all but I know from experience that you have an easier time keeping kids still on the plane when they have been allowed to move around a bit between planes.
Mama to Ethan