By Paul Rincon
BBC News Online science staff
It is difficult to appreciate now the overwhelming challenge that faced Wilbur and Orville Wright as they attempted the first powered flight on 17 December, 1903.
Air-taxis could be the aircraft of the future, Nasa says
But as the aviation industry looks towards the next 100 years, it will have to confront challenges at least as daunting as those faced by the Wright brothers.
Growth in air travel is expected to soar over the next 30 years and beyond, and there is a real possibility that the aircraft industry will struggle to keep up.
Manufacturers are also under pressure to cut noise and emissions from aircraft. Innovative new technologies may come to the rescue, but only if they satisfy a financial bottom line.
The UK Government estimates growth in passengers at around 4% per year until 2030. Industry forecasts broadly agree with this projection.
THE FUTURE OF FLIGHT?
"Occasionally, things like the Gulf War and the Sars epidemic slow that down for a short period, but then it goes back up to the same level roughly a year later," says David Velupillai, regional spokesperson for European aircraft manufacturer Airbus.
"Looking to the future, passengers will double every 15 years and triple every 23 years."
Airbus's response to the challenge posed by rising demand is the A380 - a king-size double-decker aircraft able to seat a total of 555 passengers, about 155 more than current jumbos. The A380 will house a lounge, a bar, showers and a gymnasium.
This "super-jumbo" is primarily designed for heavily travelled routes such as London to Singapore, London to New York and Tokyo to Los Angeles.
Airbus's A380 jet is the first fully double-decked aircraft
But at US space agency's (Nasa) Langley Research Center in Virginia, US, researchers have been working on a different vision for the future of aviation.
The Small Aircraft Transportation System (Sats) offers an alternative solution to the problem of burgeoning demand for air travel.
Sats, its originators suggest, would divert pressure away from the "hub-and-spoke" model of air travel. Hub-and-spoke refers to the typically US model of passengers being processed through large "hub" airports and then on to secondary flights to "spoke" airports near their final destination.
The vision of Sats is of a nation of air travellers hopping between small airports on a point-to-point, on-demand basis in "air-taxis".
Nasa is designing new aircraft for the job: 4-8-seater passenger jets and looking further to the future, personal air vehicles (PAVs), which it says would be affordable for the general public and self-operated without the need for a pilot.
Sats aircraft would also use computer display technology called "synthetic vision". This provides a virtual map of the terrain below the aircraft. This will allow pilots to land safely in low-visibility on badly-lit landing strips at small airports.
Engine technology is at the forefront of research into future aircraft. One of the developments we are most likely to see before too long is a move to "all-electric" engines and aircraft.
Conventional aircraft engines provide thrust, hydraulics, pneumatics and electrical power. But engineers envisage hydraulics and pneumatics being replaced by electrical power.
All-electric aircraft engines would provide the aircraft with thrust and act as mini-generators to supply the aircraft with electrical power.
"This would make engines simpler and more efficient," says Martin Johnson, head of communications for civil aerospace at Rolls-Royce.
The movement towards all-electric aircraft in the commercial sector is a gradual, evolutionary process. But elsewhere, researchers have been working on a new type of engine that has the potential to truly revolutionise air travel.
Hypersonic engines or "scramjets" (supersonic combustion ramjet) would enable aircraft to travel coast-to-coast in the US in about 30 minutes and from London to Sydney in about 90 minutes.
Scramjet engines operate at speeds in excess of Mach 5 (five times the speed of sound) and have a simple mechanical design with no moving parts.
Will we be flying planes like this in a few decades?
They would also permit single-stage-to-orbit space vehicles - spacecraft that fly into space in one piece, something that might bring space tourism within the grasp of the ordinary person and not just billionaires.
Aircraft with new propulsion technology may need to be radically redesigned. One of the most popular concepts of recent years is the "blended-wing-body" design, originally conceived by aerospace corporation McDonnell Douglas.
This design does away with the traditional tube and wing design of modern commercial aircraft, instead opting for merged shape that makes it look like a flying wing.
Its advocates claim that integrating the engines, body and wings into a single lifting surface improves the overall efficiency of the aircraft.
Whether new technologies get taken on will continue to depend on the business case that can be made for them.
But meeting passenger growth and environmental targets for the future means aircraft manufacturers are taking blue-sky thinking seriously, says Johnson.
The matter-anti-matter engine is one propulsion system that has been floated among futurists in the past. But aircraft manufacturers say they're not looking at such things. Not yet, anyway.