Delta Airlines has their DASH service. Under 16 ounces, anyone can ship with them. Under 100 pounds, you will need to be a known shipper with the TSA. It's available on basically any regularly scheduled flight of theirs.

We used it on a contract job in Tennessee once, to get a replacement UPS sent. Expensive, but worth it.

all airlines have something like this. it used to be called "counter to counter"; drop off and pick it up at the airport.

my story, about 1988. we had a system in Omaha with a broken power supply (it was big, say 6U, custom voltages). there was a spare in Rapid City, and downtime was charged by the hour.

no problem, took the spare in a box to the airport. they told us it was too big for counter to counter; but a ticket could be purchased and it would be put on the plane. No, problem.

"Give me a coach ticket to Omaha." "Sorry sir, those are all sold. We do have a first class ticket available." "In that case, OK"

The box went in the cargo hold.

Yes those services exist though usually you want to send your own employee, typically a junior one.

It’s a whole industry it’s called freight forwarding, and this specific thing is the cargo division of commercial passenger airlines.

Pay the flight attendant.