"Are we there yet?" usually issues from the mouths of children. But aboard these 11 flights, even the adults pester flight attendants with such questions. U.S. News Travel sought out the most painstakingly long journeys in the sky. While some people measure length by mileage, we believe the flight's duration is much more important to travelers. After all, you only want to be stuck on a plane with strangers for so long.The numerical data below was provided by each airline.Cathay Pacific offers not one, not two, but three direct flights every day from New York's John F. Kennedy International Airport (JFK) to Hong Kong International Airport (HKG). Each Boeing 777 takes about 16 hours to reach its Asian destination. The flight's carrier, Cathay Pacific, is unfamiliar to most Americans, but it is one of the largest airlines in Asia and Hong Kong's official airline. As travel between Asia and North America steadily increases, look for an escalating number of Cathay Pacific planes in your local airport.Jumping 16 hours ahead, travelers flying from Texas Ranch Country to the Australian Outback will probably experience some jet lag. Add to that 15 hours of airtime, and the trek could be downright painful. Luckily, Qantas pampers its passengers with ergonomic seats, personal on-demand entertainment sets, three meals, and complimentary wine. Upon request, customers can also receive "dopp kits" complete with a razor, toothbrush, deodorant, and other products to freshen up on board. When travelers get restless or hungry, they can take a short walk to the self-service snack bar, which is fully stocked with free goodies.In May 2011, South African Airways began its nonstop service from Johannesburg, South Africa, to New York's JFK airport. Operating once a day, an Airbus 340-600 shuttles more than 300 passengers around the globe. During their voyage, travelers receive two full meals, one snack, and complimentary beverages, including wine and spirits. In coach, the 2-4-2 seat configuration reduces the number of middle seats that regularly appear on planes with 3-3-3 arrangements. The seat-back entertainment screen comes with lots of programming as well as instructional videos for stretching during the flight.Departing from NYC's stepsister, travelers on United Flight 79 must sit tight for 16 hours before reaching their final destination. For frequent flyers, the commute from Newark to Hong Kong can be a rough one. International flights on U.S. carriers usually receive a bad rep. Small issues (like food quality and cramped seats) that are regularly overlooked on shorter flights balloon into big inconveniences during longer trips. American carriers also tend to receive lower customer satisfaction ratings on SkyTrax. For instance, United Airlines has a 4.1 out of 10 customer review score. Be sure to consider the onboard conditions before booking a lengthy flight on an American airline.It takes four pilots and two separate flight crews to handle Delta Flight 200 from Atlanta, Ga., to Johannesburg, South Africa. The Boeing 777LR used to make this trip travels 8,433 miles between the two cities and consumes almost 40,000 gallons of fuel. Meanwhile, when it comes to needing sustenance, the plane isn't alone. On board this 16-hour-and-15-minute flight, passengers annually consume approximately 70,000 cans of soda, 100,000 bags of pretzels, 200,000 bags of peanuts, and a half-million pounds of ice. The two in-flight meals offer a taste of American and South African cuisine. For instance, one current entrée is a Lemon Spiced Kingklip, a type of fish native to South African waters.Qatar Airways operates a marathon flight route between sunny Doha, Qatar, and humid Houston, Texas. Flying westward to the United States, the journey usually takes just over 16 hours. Economy passengers receive an amenity kit with an eye mask, toothbrush, and even socks to make them feel more at home. They can also follow the "Fly Healthy, Fly Fit" guide and perform some relaxation techniques onboard, such as deep breathing and stretching. While they're not sleeping or dining, travelers can view hundreds of films on their personal 10.6-inch TV screen.From oil capital to oil capital, Emirates Airlines brings people from Dubai to Houston on a lengthy nonstop flight. Commonly called a luxury carrier, the airline prides itself on its service on and off the plane. Flight attendants conduct two meal services, while the "As You Like It" menu (which includes pizza, fruit, and chocolates) is available throughout the journey. Additionally, travelers can take advantage of the full complimentary bar to calm their nerves. On this 16-plus hour trek, there's plenty of time to try all of Emirates Airlines' offerings.Emirates Airlines runs a flight between glamorous L.A. and even more opulent Dubai. On the massive Boeing 777-200LR, passengers can choose to spend the 16.5 hours in the 216-seat economy cabin, the 42-seat business class area (that features lie-flat seats), or the eight ultra-posh suites. Each cabin showcases Emirates' unique starlit ceiling that reflects the time of day at the destination. This lighting system helps combat symptoms of jet lag. However, the price you pay for your journey might give you a headache: An economy-class ticket runs between $1,800 and $2,400, while a first-class ride jumps into the $12,700 to $14,000 range.Aside from having the most delicious food for economy travelers, Thai Airways operates one of the longest flights in the world, traveling from L.A. to Bangkok. Spanning 8,260 miles, the path of this Airbus A340-500 takes 17 hours and 30 minutes. Travelers appreciate the tasty onboard meals and congenial staff. In fact, Thai Airways receives SkyTrax's elite four-star rating, indicating a high level of customer satisfaction.From Newark to Singapore, travelers aboard this 18-hour jaunt receive some much-needed pampering. For this long voyage, Singapore Airlines (SQ) employs an Airbus 340-500. Normally holding more than 300 passengers, SQ's luxury aircraft hosts only 100 seats. But to call them "seats" is really unfair; they're more like beds. Set in a 1-2-1 configuration (one at each window and two in the middle), the reclining chairs offer immediate access to the aisle. Should you be on this flight, you'll want to get up and move around, especially in the direction of the self-service snack bar. After all, you're on the longest flight in the world by distance.Currently, Singapore Airlines operates the longest flight in the world by duration, racking up 18 hours and 30 minutes in the air in just one go. From Los Angeles to Singapore, a business-class only airplane shuttles 100 passengers halfway across the globe. Most people are surprised to learn that this trip takes longer than the airline's Newark-Singapore flight, which travels about 800 more miles. The Newark flight path across the North Pole subjects the aircraft to less wind resistance, allowing it to travel faster than the flight from L.A., which crosses the Pacific Ocean.*These figures were taken from third-party sources, as the airline was unavailable for confirmation.