IT IS a calm, slightly overcast evening at an air base in South Australia, and a curious-looking white plane has just touched down on the runway. This aircraft, a Northrop Grumman Global Hawk, has long, narrow wings, a double tail, and an elegantly sculpted fuselage. But it has no windows and no cockpit, because it has no pilot. It is, in the military jargon, an “unmanned aerial vehicle” (UAV). Nearly 24 hours after taking off from Edwards air force base in California, it has just completed the first pilotless flight across the Pacific Ocean.

What is even more remarkable is that the Global Hawk made this journey without any human intervention. “We made a historic flight with two clicks of the mouse,” says Bob Mitchell of Northrop Grumman, an aviation company, who was responsible for the aircraft's development. One mouse-click from its ground controller told it to take off; another click, after landing, told it to shut down its engine. In between, the aircraft's on-board computers handled the taxi, take-off, flight (on a pre-programmed course) and landing entirely automatically.

The Global Hawk is used for military reconnaissance, and the aircraft that flew to Australia, in April 2001, did so to take part in military exercises. Global Hawks were deployed in a combat zone for the first time in Afghanistan later that year. For reconnaissance, UAVs have many advantages over piloted planes. They can fly higher and stay aloft for longer, unconstrained by the endurance limits of a human pilot, and there is no loss of life or limb if they are shot down. But might the same technology, like the jet engine, radar, and so many other inventions initially developed for military use, also have civilian applications? Global Hawk's achievement poses a provocative question: will the airliners of the future no longer need pilots?

Prepare for take-off

Only if three conditions can be met. First, a wholly automatic pilotless airliner would have to be built and shown to be safe. Second, airlines would need a good reason to use such aircraft instead of piloted ones. And third, and most important, passengers would have to be willing to fly in them.

The first of these conditions can probably be met, if not immediately, then within a decade or so. Modern airliners are already automated to an extraordinary degree. “When auto-pilots can do something better than a human pilot, we use auto-pilots,” says Ken Higgins, vice-president of flight operations at Boeing, the world's largest aircraft maker.

In practice, that involves using auto-pilots in two situations: to relieve the workload on the crew during the long and tedious portions of a flight (auto-pilots never get bored), and to make landings when visibility is poor, typically in bad weather. This requires special equipment on the ground, and most airports have only one runway equipped for automatic landings. But it is now routine for large planes to land themselves when necessary. Indeed, on some flights, the auto-pilot may be engaged immediately after take-off, while the plane is still climbing, and then remain switched on throughout the flight and during the landing.

Automatic landings in poor visibility are safer than manual landings, and modern auto-pilots can even land a twin-engined plane on a single engine. “Most people are blissfully unaware that when an aircraft lands in mist or fog, it is a computer that is landing it,” says Paul Jackson, editor of “Jane's All the World's Aircraft”.

The one aspect of commercial flight that has not yet been automated is take-off. It would be possible, says Mr Higgins, but it would require additional guidance equipment both on the plane and on the runway. And it would require a good reason to develop and install this technology, which would be expensive. Take-off is, from the pilot's point of view, potentially more complicated than landing, because there is more to go wrong. In particular, an engine failure during take-off requires the pilot to make a split-second decision: is the plane going fast enough to get off the ground, or should the take-off be aborted?

Aircraft systems are designed to a safety standard that allows only one failure in a billion flights. To devise a take-off auto-pilot that could meet this safety standard would be technically feasible, but extremely costly, says Mr Higgins. To provide an extra safety margin, for example, it might be necessary to equip the aircraft with additional back-up systems. Whenever a new aspect of flying an aircraft is automated, in other words, it is necessary to balance the benefits with the costs. So far, it does not make sense to automate take-offs. But it could be done.

Aircraft do more than just take off, climb, cruise, descend and land, however. They must also deal with air-traffic controllers, steer clear of bad weather and avoid other aircraft, both on the ground and in the air. Could these aspects of flight also be automated?

The Global Hawk deals with air-traffic controllers in a way that is simultaneously old-fashioned and high-tech. A radio on board the aircraft links it to the nearest control tower, and a separate satellite link relays speech to and from the aircraft's operators on the ground, who thus appear to be inside the plane, even though they may be on the other side of the world. If air-traffic control asks the plane to ascend, descend, or take action to avoid bad weather, the operators can instruct it to do so with a few more clicks of the mouse. Similarly, the Global Hawk can be remotely controlled while on the ground, to make it taxi on and off runways and in and out of hangars.

Could the same approach be used with large commercial aircraft? Global Hawk is a special case in many ways. Unmanned military aircraft operate under different conditions from civilian planes, says Mr Mitchell: the air space over a war zone tends to be quite empty, rather than full of commercial jets. Global Hawk flies at high altitude, around 65,000 feet (20,000 metres), so it does not interfere with commercial aviation. While a busy military base is not that different from a large airport, co-ordinating the movements of dozens of remotely controlled aircraft, as opposed to just one, would also be a daunting task.

Passengers could be routinely travelling in pilotless planes by 2030. The big challenge is not the technology but convincing the public to get on board

As a result, more widespread use of unpiloted planes would require a complete overhaul of air-traffic-control procedures, both in the air and on the ground. But this is not as far-fetched as it seems. Proponents of “free flight” have long argued that the centralised, micro-managed system of air-traffic control should be abandoned, and individual aircraft given more autonomy, both in choosing their routes and avoiding other aircraft. Flying would, in short, more closely resemble navigation at sea. This would involve a large dose of technology, in the form of navigation and collision-avoidance systems. But it would open up the skies to far more traffic than can be handled by the current system—and it would allow piloted and unpiloted planes to co-exist more easily.

Airport procedures would also have to be dramatically revised to accommodate unpiloted planes. Someone would still need to carry out pre-flight checks and other duties. Taxi-ing out to the runway, queuing up with other planes, and taxi-ing to the gate on arrival would have to be handled either under remote control, or automatically by the aircraft's systems. Again, all this would be possible, and might get easier with the advent of new technology. But why go to all the trouble?

The bottom line

In a word, money. Airlines' single largest cost is staff wages, which consume half of a typical airline's annual revenue—far more than fuel, aircraft leasing or servicing costs. Pilots are the most costly airline workers to employ. At a typical airline, industry insiders say, 97 of the 100 most highly paid employees will be pilots.

Pilots are well rewarded, and with good reason: people trust them with their lives. Captains on long-haul flights are the most highly paid. According to Aviation Information Resources, a pilot-recruitment firm, the most senior captains earn an average of $178,000 a year. Some airlines pay far more: the most generous is Delta, which pays its top pilots $248,000.

There are other costs too, including per-diem and overnight expenses. Pilots expect to stay in fancy hotels when stopping overnight between flights. And why not? Before they take hundreds of lives in their hands, pilots ought to have had a good night's sleep. Safety considerations, which preclude pilots working too many consecutive hours, impose other costs. Airlines maintain elaborate rostering systems to ensure that there are enough pilots ready for duty, since each one can only work a few days a week. When a flight is delayed, the pilot may find that proceeding with the flight will require him to work more than the permitted number of hours; so a new pilot must be found, or the flight cancelled.

Automating flights completely would, of course, do away with these costs. Auto-pilots are amenable types: they never get tired, demand pay rises, go on strike, or drink too much. It would require lots of expensive new systems, but if it could be made to work, the cost savings would be enormous: billions of dollars a year for a large airline. Even partial automation, perhaps involving shifts of pilots looking after several semi-autonomous aircraft at once via remote control, would save money. Again, Global Hawk points the way: a single operator can control two or more aircraft from the same command console on the ground. And research by Boeing, which is building an unmanned fighter aircraft for the American air force, suggests that operators could efficiently control up to four aircraft at a time.

None of this is likely to happen any time soon, of course. But the technological trend is clear. Craig Mundie, chief technical officer at Microsoft, the world's largest software firm, estimates that passengers will routinely travel in pilotless planes by 2030, a claim he has backed up with a public bet to that effect (see www.longbets.org/bet/4). For his part, Mr Mitchell believes it is unlikely to be before 2050, but that it will happen eventually.

In the meantime, there may be nearer-term opportunities for unpiloted planes. Northrop Grumman is examining commercial uses for unpiloted aircraft including surveillance, communications—a drone aircraft flying over a city could act as a low-altitude communications satellite—and even crop-dusting. In November 2001, Boeing set up a dedicated unmanned-systems unit, which will initially concentrate on military aircraft, but with the aim of transferring the technology into civil and commercial aviation.

Assuming they can prove themselves in small commercial applications, the next big step would be to use unmanned aircraft for freight. Federal Express has discussed this possibility with Mr Mitchell. If unpiloted freighters then became commonplace, the way would be clear to consider passenger flights. And at that point, advocates of unpiloted planes would face their greatest challenge: convincing the public to get on board.

That could be a tall order. For while it would be possible to make a case for pilotless planes on safety grounds, this would mean pointing out some of the hazards associated with piloted flights. No aircraft maker or airline is going to do that.

Yet more than half of air-travel deaths are the result of “controlled flight into terrain” (CFIT), which is industry-speak for “the plane was working perfectly, but the pilot flew it into the ground”. CFIT accidents cause the most casualties because few passengers survive them. People are far more likely to survive if a plane overshoots a runway, or its landing-gear collapses, than if it flies into a mountain. Of the 18 fatal air accidents in the first half of 2002, nine are thought to have been due to CFIT, resulting in 397 deaths.

Other forms of pilot error can also be fatal. On July 1st 2002, two planes collided over Germany, killing 71 people. The airborne collision-avoidance system worked perfectly, but human error, both in the air and on the ground, meant the collision happened anyway. It would be foolish to suggest that unpiloted planes would never crash or go wrong. But a few years of data from unpiloted freight flights would make meaningful comparisons possible, and might favour more automation.

Another problem with advocating unpiloted aircraft as a means of reducing pilot error, however, is that it would mean drawing attention to the realities of air safety—a subject the industry seems keen to avoid, with the tacit approval of passengers. No large airliner has ever made an emergency landing on water, for example. The engines, which hang in “pods” beneath the wings, make such a landing almost impossible, notes Mr Jackson. So the life jackets, with their little whistles and lights that come on when in contact with water, have little purpose other than to make passengers feel better. Yet airlines and passengers seem happy to pretend that there is some point in having them.

Similarly, there is abundant evidence that rear-facing seats are safer than forward-facing ones in the event of an emergency landing. But any airline that made all its seats rear-facing would probably go out of business, because most people prefer facing forwards. Only soldiers, who have no choice, routinely travel in aircraft with rear-facing seats. The rest of us, it seems, put comfort above safety, or would rather not be constantly reminded of the possibility of an emergency landing.

Come fly with me

Promoting pilotless planes on the basis of safety is a non-starter, then. But there might be other approaches. One is pricing. Many people who said they would never fly again after the September 11th attacks changed their minds when the airlines slashed their prices. Another approach would be to phase in unpiloted planes gradually. At first, automatic flights could be made with a single pilot on board, until the idea had become generally accepted.

This gradual approach has worked well in promoting the use of twin-engined aircraft on long routes, another technical innovation that was once regarded as unthinkable. Long-haul flights used to be done with four-engined planes; if one engine failed, the aircraft lost only 25% of its propulsion. Today, says Chet Ekstrand of Boeing, most people do not even notice how many engines their aircraft has. The choice of airline and aircraft, he says, “is overwhelmingly about comfort, price and schedule convenience.”

Originally, says Mr Ekstrand, it was the airlines which came up with the idea of long-range twin-engine aircraft. The manufacturers and airlines then worked together to promote the idea to regulators, pilots' associations, and passenger groups. Initially, twin-engined aircraft on long routes had to ensure they were never more than 60 minutes away from an airport in the event of an engine failure. Once the reliability of twin-engined aircraft was established, the time limit was increased to 180 and, recently, to 207 minutes.

Passengers are also more likely to accept pilotless planes once other forms of transport have been automated, suggests David Stempler, president of the Air Travellers Association, an American organisation which represents passengers' interests. People are quite happy to travel in automatic lifts; and while rail travellers say they prefer to have a driver on board, the few examples of driverless trains that do exist do not seem to have any fewer passengers. As long as there is someone standing ready to take over in the event of a problem, says Mr Stempler, he sees “no extraordinary impediment” to passengers eventually accepting pilotless planes.

Indeed, the standby pilot need not even be on the aircraft. After September 11th, a number of industry observers suggested that it ought to be possible to take control of aircraft from the ground, to deter hijackers. So, says Mr Stempler, the notion of remote control is “starting to percolate”. Passengers might be happy to accept it as an anti-terrorism measure initially, and then get used to the idea. It would take only one incident to change attitudes to remote control dramatically, one way or the other.

In other words, it is still far too early to tell how passengers would react to the idea of fully automated flights. The technology and the economics seem to make sense. But ultimately, it will be up to passengers to decide whether pilotless airliners will ever get off the ground.