The guy was an Islamic male. He has been raised to be intolerent of "loose" women, "forward" women, Western women.
He was being polite at the gate because he is male and it is his perogative to be polite if he chooses (not hers, she's a woman). He is Muslim. He's the boss.
Later on the plane, this woman gives him a big smile. Is she "loose"? Has she no morals? Is she a prostitute? He is completely aghast. It's not on his cultural map.
So he gives her a stoneface.
Do you now consider it explained?
That is an incredibly lame explanation.
And a very bigoted one about Muslims.