The Pan Am smile is the name given to a fake smile, in which only the zygomatic major muscle is voluntarily contracted to show politeness. It is also known as...

The Pan Am smile, also known as the "Botox smile", is the name given to a fake smile, in which only the zygomatic major muscle is voluntarily contracted to show politeness. It is named after the now defunct airline Pan American World Airways, whose flight attendants would always flash every passenger the same perfunctory smile. Botox was introduced for cosmetic use in 2002. Chronic use of Botox injections to deal with eye wrinkle can result in the paralysis of the small muscles around the eyes, preventing the appearance of a Duchenne smile.

The Pan American smile is a perfunctory smile. It is nothing but a courtesy smile as in the case of a flight attendant responding to a patron. It's an expression of courtesy and politeness rather than inner joy. Alas, the Pan Am airline is dead but the smile will live forever.