With ever-improving fuel efficiency and aerodynamics, planes are able to stay in the air for longer than ever before. All major airlines have extended-range aircraft that can make a leg-cramping 14-hour flight with no problem. A few commercial carriers have even been able to stretch their time aloft to more than 18 hours.

Because of wind patterns, route paths, air traffic and other factors, flights that cover the longest distance do not necessarily take the longest amount of time. Favorable west-to-east tailwinds, for example, can make a journey from Sydney to Dallas an hour faster than the exact same trip in the other direction.

For fliers, time in the air is what matters the most. About 16 hours in economy class will give you the same amount of “seat numbness” no matter how much distance you’ve covered. Most passengers answer the question “how bad is it going to be?” by glancing at the “flight duration” figures on their itinerary.

So what are the longest flights in the world in terms of time in the air?

The long hauls from the Middle East to New Zealand

Auckland Airport welcomes the first Qatar Airways flight with a traditional water cannon salute Auckland Airport welcomes the first Qatar Airways flight with a traditional water cannon salute. (Photo: Qatar Airways/Facebook)

Holding the number one spot as of February 2017 is Qatar Airways. The airline rolled out a regularly scheduled flight between its hub in Doha, Qatar, and Auckland, New Zealand. The flight covers 9,032 miles, and is in the air for 16 hours and 10 minutes for the Auckland-bound leg. If you're flying to Doha, however, prepare for an even longer flight. Due to strong headwinds, the flight to Doha will take 17 hours and 30 minutes.

The Boeing 777 flight has 42 seats in business class and 217 in economy. While every passenger gets to enjoy individual screen entertainment offerings during the flight, those 42 folks in business class also have "fully-flat beds" seats and an on-demand food menu available at all times. (No waiting for the drink and snack carts in business!)

With its first flight taking place on Feb. 5, Qatar Airways' flight to Auckland beat Emirates's Dubai-to-Auckland flight for the longest flight. The Emirates flights from Dubai to Auckland covers 8,819 miles in just under 16 hours and 17 hours and 15 minutes in the other direction. That non-stop flight will also use a Boeing 777.

Asia to the U.S. in a less than day

An Air India Boeing 777 takes off from San Francisco International Airport. Air India's flight to San Francisco covers 9,400 miles. (Photo: Bill Abbott/flickr)

But what about flights not out of the Middle East to the land of the kiwis? How do they measure up?

For sheer distance, Qatar loses out to Air India's Delhi to San Francisco flight. Previously a flight that took a shorter polar route, the airline changed things up in the fall of 2016 and now flies over the Pacific Ocean, making the previously 7,700-mile flight now 9,400 miles. Why the change? The tailwinds allow the flight to get to its destination two hours quicker than the polar route. And it probably won't surprise you at this point to learn that the flight also uses a Boeing 777.

All these flights would have paled to Singapore Airlines' old flights from Changi Airport to Los Angeles and to Newark, New Jersey. The Singapore-Los Angeles flight jetted across the Pacific and landed after 17 hours in the air while the flight to New Jersey would go over the North Pole and would clock in between 19 and 21 hours. Both flights were cancelled in 2013 due to rising fuel costs and an aging fleet of long-haul planes. However, the airline announced in October 2015 that it would begin non-stop flights to Los Angeles and New York City starting in 2018. The airline won't be using the Boeing 777 — surprise! — but will instead use the "ultra long-range" version of the Airbus A350.

The planned flight from Singapore to New York will cover just over 9,500 miles, which would make it the longest flight in terms of mileage in the world.

The longest of the rest

A Qantas airplane at Dallas-Fort Worth International airport Flying from Dallas, Texas, to Brisbane, Texas, on Qantas involves one layover, and the result is a 19-hour trip across a few time zones. (Photo: ERIC SALARD/flickr)

Even if it loses in longest flights to Qatar, Emirates still has couple of flights out of Dubai that cross the 16-hour line. Its flights to Houston Intercontinental in Texas and to Los Angeles both take longer than 16 hours and cover more than 8,000 miles.

Australia's flagship carrier, Qantas, is also in the ultra-long-haul market. The airline offers two flights longer than 8,000 miles between Australia and Dallas-Fort Worth International Airport: one from Sydney and one to Brisbane. The DFW to Brisbane trip crosses the 19-hour threshold, including a single layover, but the flight that originates in Sydney is a non-stop one that takes a mere 15 hours to reach its north Texas destination.

One final service that deserves mention in the behind-numbing flight category is from taking Delta from Atlanta's Hartsfield-Jackson International Airport to Johannesburg. The outbound journey from Atlanta tops out at just more than 15 hours; the return trip breaks the 17-hour barrier.

Long in-country flights

An American Airlines Boeing 737 landing in Miami Strap yourself in for the American Airlines flight from Seattle to Miami. (Photo: BriYYZ/flickr)

If you don't plan to travel abroad, reading about these long air journeys should make you feel better about the amount of time you spend on domestic flights. The longest routes within the U.S. are between the East Coast and Hawaii. Non-stop flights from New York's JFK to Honolulu on United and Hawaiian Airlines take more than 11 hours.

The longest routes in the lower 48 are between Florida and Seattle. American Airlines flies to Sea-Tac International Airport from Miami, while Alaska Airlines flies to Fort Lauderdale. Both flights are aloft between 5.5 and 6 hours. United, JetBlue and Virgin America are close runners-up. These three carriers offer seven-hour service on the heavily traveled Boston to San Francisco route.

This story was originally published in September 2014 and has been updated with new information.