An Emirates Airbus A380 jet has made the longest (by distance) commercial non-stop flight [bbc.com], covering a distance of about 14,200 km in around 17 hours and 15 minutes:
Qantas' Dallas-Sydney flight was believed to be the previous current longest flight, at 13,800km and clocking in at about 16 hours, 55 minutes.
The Dubai-Auckland flight duration record is not expected to hold for long, as Emirates is launching a Dubai-Panama City service later in March that will take 17 hours, 35 minutes. Singapore Airlines used to fly Singapore-New Jersey, which took 19 hours. The firm announced in 2015 it was planning to bring back the service in 2018.
The new non-stop Emirates route between Auckland and Dubai reportedly reduces the current travel time by three hours.