The fierce sales war between arch rivals Airbus and Boeing will be reignited next week with the opening of Farnborough, the year's biggest air show.

Attention is likely to focus on Airbus and its plans for an all new mid-sized airliner to challenge Boeing.

Airbus is facing mounting pressure to reveal details of its new design, which analysts say could cost as much as $10 million (£5.4 billion) to build.

John Leahy, Airbus's top salesman, will be working hard to sell the concept and could have deals to announce at Farnborough when it opens on Monday.

Airbus has wrestled for more than a year with the design of the A350 - but some analysts believe the aircraft could now be shelved as the company responds to calls from potential buyers looking for an even more advanced airliner offering greater fuel efficiencies.

Credit Suisse analysts wrote in an research report yesterday: "It looks increasingly likely to us that Airbus will scrap plans for the A350 aircraft and launch a brand new A370."

Former joint EADS chief executive Noel Forgeard had said at the Berlin air show in May that decisions would be made on the A350 by Farnborough.

But Mr Forgeard resigned at the start of this month, having lost a bitter struggle to keep his job after Airbus announced further six-month delays to deliveries of the A380 superjumbo.

On Tuesday EADS co-chief executive Thomas Enders conceded that Airbus had underestimated Boeing in terms of orders, but vowed: "The picture is going to change."

The previous day Airbus admitted that aircraft sales plunged by more than half in the first six months of this year to 117 mainly single-aisle planes, down from 276 in the year-earlier period.

That compared with 480 orders for Boeing, boosted by the success of its 787, up from 441 a year earlier.

But Mr Enders said: "The problems at Airbus do not mean we are a restructuring case."

He added that the delays to the A380 had not yet prompted any airline customers to cancel orders for the aircraft, the world's largest passenger plane.

Boeing's 787 has yet to take to the skies. However, the aircraft could create some excitement at Farnborough if the US planemaker announces plans to build a bigger version, dubbed the 787-10.

If that announcement comes, it is likely to include the name of a launch customer, taking a potential deal away from Airbus.

Boeing watchers will also be looking for the unidentified customer listed on the company's website as the first buyer of the latest and largest version of the 747 jumbo, the 747-8 Intercontinental.

Meanwhile, Embraer is set to fly its 190 airliner at Farnborough, one of its largest models at 108 seats and part of the Brazilian planemaker's foray into the niche just below the model ranges of Airbus and Boeing.

On the defence side, Boeing's F-15 and F/A-18 fighters will be on display, as will the Lockheed Martin's F-16, the Eurofighter Typhoon, the Gripen from Sweden's Saab and Russia's MiG 29.

Lockheed Martin will give a briefing on the F-35 Joint Strike Fighter (JSF), which is the subject of some controversy in the UK and elsewhere as governments demand work and technology from the $276.5 billion (£150.2 billion) project before committing to big orders for the futuristic fighter plane.

Raytheon will show off the UK's newest spyplane, the Sentinel R1, which adds a sophisticated radar system to a Bombardier Global Express business jet.

Spyplanes and combat jets without pilots, called UAVs (unmanned aerial vehicles) and UCAVs (unmanned combat aerial vehicles), will also be on display.

Italy's Alenia Aeronautica will display its Sky-X UCAV and Europe's biggest defence company, BAE Systems, is expected to give more details on its work on the UAV/UCAV programme.

The US Air Force will be flying several aircraft at the show.