Typically, during a 14-hour flight, the captain and first officer will fly the first three hours. Then, they hand off the plane to a second crew and get some rest in a special compartment -- or in reserved seats in the passenger cabin.
During the cruise portion of the longhaul, pilots use various methods to keep sharp, such as checking fuel consumption and navigation, adjusting the ventilation, turning up cockpit lighting and engaging in energetic discussions with the other pilot.
Every three hours, the two crews will switch off command of the cockpit until about 90 minutes before landing, when the captain and first officer will land the aircraft.
So, those are some of the ultralonghaul challenges for humans. As for the machines -- they have their own hurdles.
Obviously over vast oceans it's critically important for airliner engines to be reliable and powerful. But hey, it's a business, so the engines also have to be efficient enough to keep airline fuel costs low.
Decades ago, that meant ultralonghaulers were likely four-engine planes, like the 747. In the unlikely event that an engine failed, the other three engines could power the plane the rest of the trip, no problem.
The downside: Four engines guzzle a lot of fuel.
"Now, engines are way more reliable," says travel expert and former airline manager Brett Snyder of CrankyFlier.com. They're also more powerful and fuel-saving.
That's why Boeing's twin-engine 777 Worldliner flies so many of the world's longest nonstop routes.
In the coming years look for newer wide-bodies to fly more longhaul routes, like Boeing's twin-engine 787 Dreamliner and the twin-engine Airbus A350 XWB. Both aircraft are made with superlightweight materials which also cut down on fuel costs.
Already, United Airlines has announced its Dreamliners will begin 14-hour nonstop service from San Francisco to Chengdu, China. British Airways plans to use the plane for a 10-hour nonstop from Austin, Texas, to London.
The FAA requires twin-engine planes to fly within close reach of a safe landing spot, in case of engine trouble.
If a 777 lost one of its two engines, the plane has a computer that automatically adjusts the aircraft's controls to compensate for unbalanced thrust. Pilots flying other airliners may have to manually adjust the plane to compensate.
How reliable are those engines?
"We've never seen an issue where a twin-engine plane has lost one engine and can't make it somewhere with the other engine," says Snyder. "And engines almost never fail. With high reliability, airlines are free to look at economics and say, 'Why would we have aircraft with four engines when we can have one that performs the same mission with two and save us money?'"
What killed the longest flight in the world?
In fact, money is exactly what's being blamed for killing the longest flight in the world.
That's right -- after nine years of service, Singapore Airlines Flights 21 and 22 are scheduled for cancellation.
Snyder and most other experts suspect the airline got tired of dealing with poor profit margins on the fuel-guzzling four-engine Airbus A340. "They do use a ton of fuel, and that's always painful," says Snyder. "But the schedule advantage isn't that great either when you fly so far."
Also, the world's second-longest nonstop -- a Singapore Airlines 18-hour flight between Singapore and LAX -- is scheduled to be canceled this month.
That will leave Qantas Flight 7, a Boeing 747 from Sydney to Dallas, atop the list of world's longest nonstops by distance, at 8,600 miles. The longest nonstop by time will be Delta's Flight 201 -- a 777 from Atlanta to Johannesburg which clocks in at about 17 hours.
Fans of the Singapore-Newark flight say they'll miss its spacious seats and well-trained flight attendants.
The way Amex exec Uriarte sees it, for now, the airline industry appears to have pushed the longhaul envelope to the maximum.
"That's about as long as we're going to get," he says. "The days of the 19-hour flight are over."