Babies crave input! And visual input is most easily accessible to them.
They get bored with mom after a while, and strangers are a shock to their input stream, so they really respond.
Eye contact is the essential element, because they are aware of self, and crave attention.
They also respond in kind: smile and they'll smile back!
I've spent a *lot* of time on airplanes, and I do what you describe all the time, and it does indeed work!
Babies also have really sensitive ears, so between the noise and the air pressure drop, crying on the airplane is inevitable. I only took a few trips with mine when she was small, mainly because I didn't want to put *her* through it (with all the jerks I meet on planes, I didn't really care much how *they* would react!). And the one long trip we took, I made sure to get first class seats so she had a whole row to crawl around in.
That’s the miracle of babies, their ability to lay bare the tender, beating hearts of raging a**h***s,

Buffy