India on Monday began the trials of fighter jets being hawked by the world's six top aerospace giants vying for a 12-billion-dollar military contract, officials said.

The sale of 126 combat planes to the technology-starved Indian Air Force will be the world's most lucrative fighter jet contract in more than a decade.

Military air traffic controllers said Boeing kicked off the trials with a display of its F-18 "Superhornet" jets in Bangalore, hub of India's aeronautical and space industry.

"Two F-18s carried out two sorties of 45 minutes each," a controller said as military aviation experts watched the exercise.

The assessment is due to continue for almost a year before New Delhi makes its choice from the six companies, defence ministry officials in New Delhi said.

Lockheed Martin of the US and Europe's EADS will be among the other five firms descending on Bangalore.

India is on a spending spree to update its largely Soviet-era weapons system.

After Boeing, Lockheed Martin is next in line to showcase its F-16 to the technology-hungry Indian Air Force, the officials said.

The European Aeronautic Defence and Space Company (EADS) will offer its Typhoon Eurofighter, while Russia is seeking to sell the MiG-35 and MiG-29.

French Dassault, which constructs the Mirage, has put forward its Rafale aircraft as a contender.

The line-up is completed by Gripen, part of Sweden's Saab.

Industry sources have said Lockheed Martin and Boeing have emerged as frontrunners.

Contract stipulations prevent the contending firms from unveiling any detail of the contract, which includes the outright purchase of 18 fighter jets by 2012 and another 108 to be built in India.

India also has an option to buy 64 more jets.

The Indian Air Force, the world's fourth-largest, is also spending 1.6 billion dollars to buy 40 Russian Sukhoi fighter planes by 2010 and is shopping for hundreds of helicopters and transport planes.