In the past I’ve tipped anywhere from $5 to $20 depending on how long they spent with me. $5 would be just going from the gate to the curb at a relatively small terminal like PDX or SFO. $20 would be going through passport control or dropping off and later picking up at a lounge at a larger airport like JFK or ATL.

That said, tipping is highly personal and subjective, so I’m sure someone will say I’ve been way too stingy and someone else will say tipping shouldn’t be considered a requirement at all.