The 10 longest flights in the world, ranked

• Ultra-long-haul flying is back with a vengeance thanks to new planes and cheap oil.
• Qatar Airways, Qantas, and United have all recently launched new ultra-long-haul flights.

After the financial crisis all but wiped out ultra-long haul flying, the ultra-long-haul flying isn't just back, it's back with a vengeance.

The resurgence in these 8,000 to 9,000-mile marathon flights can be attributed to the availability of affordable oil and a new generation of fuel-efficient airliners like the Boeing 787 Dreamliner and Airbus A350. In addition, the change in consumer preference in favor of non-stop point-to-point flying has helped drive this revival.

Last year, Qatar Airways launched the longest flight in the world between its home base in Doha, Qatar and Auckland, New Zealand. At Emirates, upgraded its flight from Dubai in the United Arab Emirates to Auckland from a Boeing 777 to an Airbus A380. It's now the third longest flight in the world and longest operated by a superjumbo.

United has relaunched non-stop service from San Francisco to Singapore, the longest flight operated out of the US while Qantas is going non-stop between Perth in Western Australia and London.

There's so much going on in ultra-long-haul flying that Business Insider turned to air travel intelligence firm OAG for the authoritative list of the long flights in the world.

Here are the 10 longest flights in the world ranked: