Single-aisle jets are not supposed to be long-haul workhorses, but the Airbus A321neo has steadily pushed the boundary of what narrowbody range can mean. With new-generation engines, aerodynamic tweaks, and smarter cabin densification, the Airbus A321neo lets airlines open thinner routes, add frequency in premium-heavy markets, and right-size capacity where a widebody would be too large. For the major US airlines, it has become a core tool for network planning, as it links hubs to high-yield leisure destinations, stretches transcontinental flying, and, in some cases, tests the outer edges of stage length that can still make both operational and financial sense for a carrier.