Here's what he means: Improved technology has contributed to shrinking cockpit staff. According to Hansman, before the Boeing 757 began service in the 1980s, most large airliners had a standard flight deck staff of three. They were the pilot, co-pilot and a flight engineer who managed pressurization, heating, fuel and pneumatic systems. Then, Hansman said, "those systems became automated, and the standard flight deck crew went from three to two."
Going from two to one pilot would be a difficult threshold for the airline community to cross. Two onboard pilots allow for a safety net -- a redundancy, he said -- to ensure sound judgment calls and to protect against possible incapacitation of the pilot -- for example in case of sickness or an accident.
But going from two to zero is another thing altogether.
"It's not clear that anybody would want to ride on an airplane that doesn't have a crew on board," Hansman said.
Would Hansman? No.
"Not at this point," he said.
No matter how trustworthy the technology becomes, Hansman said remote-controlled airliners will never become reality without widespread public acceptance.
But he doesn't rule out that possibility.
"You have to remember, nobody thinks twice about getting onto an automated train, for example, at the airport."
This isn't all conjecture, though. To be sure, unmanned aircraft are coming soon to airspace near you.
In fact, it may not be long before you see remote-controlled drones flying over your neighborhood.
The Federal Aviation Administration plans to begin flight testing and writing rules aimed at integrating unmanned aircraft into the national airspace system as soon as 2015. Some of these might include flying drones with sophisticated cameras like the Draganflyer, which can be used for police search and rescue, or unmanned crop-dusters. By 2018, the nation's unmanned aircraft could number more than 15,500, according to industry projections.
Aerospace contractor Northrop Grumman is developing an unmanned combat jet the size of a fighter plane.
If successful, the X-47B would claim two firsts for an unmanned jet: in-flight fueling capability, and launch and landing aboard Navy aircraft carriers.
For Sullenberger -- perhaps the nation's most famous pilot -- the idea of remote-controlled airliners triggers a lot of critical questions.
He speculated about what might have happened to Flight 1549 after it collided with the geese if the plane had been controlled by a remote pilot.
"What if the geese damaged whatever forward viewing devices there were -- such as cameras or infrared or radar? What if the damage prevented the operator from seeing the river? Or seeing the plane's height above the river?" How would the operator be able to land the plane safely?
"On every airplane I've ever flown, I tend to use the technology to its full capabilities when it's appropriate," Sullenberger said. "But looking as far into the future as I can see, every airplane -- no matter how sophisticated -- really needs to be flown, and flown very well, by a human pilot."