A jetliner is a large jet plane that carries many passengers — the kind that fills a gate at an airport, not a tiny private jet and not a fighter. Airliner is the everyday cousin; jetliner just makes it clear the plane uses jet engines. News, airlines, and people who like planes use it. You would not call a small propeller plane a jetliner, and you would not usually call a private business jet one either: the picture in people's heads is a big public passenger aircraft.