Boeing's super-jumbo to take off first

Thai Airways and Malaysia Airlines have signed letters of intent to purchase the planned stretched "super jumbo" version of the Boeing 747 capable of carrying nearly 600 passengers.

It is an important breakthrough in the battle between Boeing and Airbus for supremacy in the very large aircraft market, which could be worth up to $200bn (pounds 120bn).

With launch customers now lined up, Boeing will be able to press ahead with developing stretched versions of the 747-400, which it hopes to have in service within four years.

The two aircraft manufacturers were unable to agree on a collaborative approach to a new super jumbo and are offering rival versions to customers.

Neither manufacturer has, however, been able to persuade British Airways to make a commitment. BA has been a supporter of very large aircraft but the company has put on hold its plans to add the super jumbo to its fleet until its plans for a widespread restructuring are completed.

Boeing has chosen to stretch the 747-400 model, which can carry around 400 passengers, and is offering 747-500 and 747-600 models to potential customers, which will carry between 460 and 600 passengers.

Boeing's designs are further advanced than those of Airbus, which should enable its planes to be in service up to four years earlier.

Airbus is planning a new A3XX double-decker aircraft, which could ultimately carry up to 800 passengers. It is developing the aircraft from scratch at a cost of $8bn. It will not be in service until at least 2004.

Airbus argues that customers should wait as its plane will be cheaper to run.