It seems as if the big competition among airlines these days is for the longest flight, which is probably the flight that most passengers are not looking forward to. Singapore Airlines is the latest with a claim; in October it will re-open a direct route from Singapore to New York/Newark.
Like many of the extreme-length flights announced recently, it's made possible by a new plane and new technology, in this case an ultra long-range version of the Airbus A350. Long-range variants of the A350 and Boeing 787 have accounted for the changes; as fuel-efficient long-range planes they have made possible many new routes.
For Singapore, the 18 hour 45 minute flight will be in addition to the airline's flight that stops over in Frankfurt. The airline previously flew the New York route directly, but dropped it because it couldn't make money using its four-engine A340s.
Part of what makes the extreme route possible is to keep the plane's load light; the version to be used on this route has only 161 seats, 67 in business class and the rest in premium economy.