seatmate

plural seatmates

1. One who shares a seat (such as a bench or other surface that seats more than one).
2. One who sits next to another.

   My seatmate on the airplane snored incessantly.

   3 more examples

   The Buzzis' older son, Rocco, and I had been high school buddies, then roommates at BU, seatmates at Sox games.

   2008, Wally Lamb, The Hour I First Believed, Ch.1, at p.15

   Last month, the cryptographer and coder known as Moxie Marlinspike was getting settled on an airplane when his seatmate, a Midwestern-looking man in his sixties, asked for help.

   2020 February 14, Andy Greenberg, “Signal Is Finally Bringing Its Secure Messaging to the Masses”, in Wired

   Several years ago, I was sitting on a flight to San Francisco, when my seatmate, a man a little older than me, struck up a conversation. Perhaps you hate it when that happens; I love it.

   2021 January 14, Arthur C. Brooks, “Find the Place You Love. Then Move There.”, in The Atlantic