If ever you are find yourself on an airplane next to a screaming baby and you think to tell the mother struggling with the screaming child that "having a bottle or pacifier to suck on helps their little ears"...
Believe me. They have already heard this advice at least ten thousand times before they even set foot on that plane. Suggesting this is not helpful. It serves as nothing more than a petty insult to the mother's knowledge of her own child and proclaims your dislike of being stuck next to a kid on your flight. How very classy and helpful of you to add irritation and stress to an already irritated and stressed-out mom.
Perhaps instead you might try something like, "Your baby is so sweet! Poor little thing. You sure do a great job traveling with him/her."
But before saying the above nice comment, take note of whether the baby is wearing pink. Any pink at all. If so, you can pretty safely assume it's a girl.
Just thought I'd throw that out there.