IF you're familiar with blue whales, then the boast that the new Airbus superjumbo is about as long as two of them put together will strike a chord. If, however, blue whales don't feature regularly in your life, then you'll just have to accept that we're talking big.

Size clearly matters to Airbus, the European consortium which has broken Boeing's stranglehold on the passenger aircraft market. At 73 metres long and 24.1 metres tall, its new A380 is the largest civilian plane in existence. Its wingspan, of 79.8 metres, is just ten metres short of a football pitch.

But the A380, already nicknamed superjumbo, is not just there to claim a place in the record books. According to Airbus, it will change the market for long-haul flights forever.

When the Boeing 747 arrived in the 1960s, it promised a revolution in air travel. Able to carry more people at a lower cost than its predecessors, it opened up air travel to a new market.

The A380, launched in Toulouse amid dancers and dry ice yesterday, is heralded as the most significant development in air travel since the 747. It can carry a third more passengers, 555 compared with the 747's 400, and consumes less fuel per passenger than its rivals, meaning fewer flights will be needed to carry the same number of people at a lower cost.

With the demand for air travel expected to soar over the next 30 years - the UK Government is expecting growth of four per cent a year until 2030 - the A380 could be crucial in ensuring airlines are not left struggling to cope.

But it is not just in its size that the A380 marks a new phase in the history of flight. The double-decker aircraft promises to offer in-flight shops, a lounge, showers, bars and a library. Virgin Atlantic, one of 11 airlines which have already agreed to buy the plane, is talking of installing a casino and gym. Lufthansa, Qantas and Malaysian Airlines are also among the carriers to have agreed to buy the new plane, with Emirates its largest customer, ordering 45, and Singapore Airlines due to take delivery of the first one next year.

The plane cost around £6bn to develop but its makers, a consortium of British, German, French and Spanish aerospace companies, are confident this will be recouped. With a break-even figure of 250 planes, 149 have already been ordered, and Airbus is predicting more than 700 will be sold in total.

But not everyone is banking on the big is beautiful approach to air travel.

Boeing, which dominated the civilian aircraft market until the arrival of Airbus, had been locked in a race with its rival to produce the superjumbo, but abandoned the idea in 2001 and is now focusing on developing smaller aircraft, capable of flying to more destinations.

The 7E7 Dreamliner is designed to replace the ageing 757 and 767 planes and will enter service in 2008, two years after the A380 carries its first fare-paying passenger. With 230-300 passengers, the 7E7 will be more flexible than its Airbus rival, but capable of flying long as well as short-haul.

For Boeing, the decision to go in the opposite direction to Airbus came after taking soundings from airlines, who suggested there would be little demand for superjumbos. Instead, airlines were moving towards smaller aircraft, such as the 777, with fewer seats but able to provide more regular flights.

The US space agency NASA is working on an even smaller approach to air travel, looking at the possibility of developing eight-seater jets which would hop between small airports on demand, diverting pressure from the hub airports.

British Airways is one of the carriers which has said it is not buying the new Airbus, despite being one of the original 20 launch partners of the project. Its strategy is to reduce capacity and buy smaller, long-range aircraft, although it has not ruled out changing its mind.

Boeing talks of problems of congestion which may limit the market for superjumbos, although Airbus has dismissed this as the talk of a rival which is now playing catch-up after years of unchallenged supremacy.

The bitterness has even spread to the respective governments, with the US threatening to take the European Union to the World Trade Organisation, alleging illegal subsidies had been paid to Airbus. The two agreed to bilateral talks after the EU claimed the US was itself paying illegal subsidies to Boeing.

But if much of the sniping can be put down to the struggle for market supremacy, there is cause to question Airbus' faith in the superjumbo.

Although a normal configuration would mean 555 seats spread across four aisles, the A380 has the capacity to seat around 800, with critics suggesting that its three classes - first, business and standard - could be replaced by just one, cattle.

The A380 will also be limited in where it can land. Its size means it will only be able to fly into the 60 larger hub airports, with anyone wanting to fly to a smaller airport forced to catch a connecting flight. Heathrow and Charles de Gaulle airports are among those which have had to make special adaptations to accommodate the aircraft, with Heathrow's changes including a double-decker passenger ramp and larger baggage conveyors.

More passengers also means there is a greater possibility of delays, as they are processed through security and then boarded. The longer the aircraft spends on the ground, the less money it can make. There are also doubts over whether people will want to fly with as many as 550 other passengers, much less the possible 800.

But Airbus is gambling on its superjumbo taking off, and not just at the test flight scheduled for April. With operating costs 20 per cent lower than the 747, and capacity to take 35 per cent more passengers, it is trumpeted as the more environmentally friendly way to cope with the expansion of air travel.

Now the question is whether airlines, and passengers, will plump for the build-it-big A380, or its small-is-beautiful rival, the Boeing 7E7. The answer will determine whether the superjumbo turns out to be a soaring success, or a white elephant. Or even a white blue whale.