Though the tender is for 126 aircraft, there is an option for an additional 50 percent, or 63 more aircraft.

The F-16 trials will take place a fortnight after Boeing flew in its two Super Hornets Aug 14 and conducted trials for about 10 days from Aug 17 in Bangalore before taking-off to Jaisalmer and Leh for a series of trials in hot and cold weather conditions.

During the second round of field trials, senior IAF test pilots will join Lockheed Martin test pilots to fly the tandem-seater fighters for a firsthand feel of its capabilities and technologies, especially its electronic warfare abilities.

'Initially, the IAF pilots will co-pilot the aircraft, taking controls mid-air after familiarising themselves with the systems and the advanced navigation aids. In the subsequent trials, the IAF pilots will take command of the aircraft for evaluating its various parameters, including use of weapons,' a Lockheed Martin official said but declined to be named.

The IAF has formed two teams of two test pilots each for the flight trials, which will be conducted in three stages: pilot familiarisation, field trials and weapons systems trials. The third stage will be conducted in the country of manufacture.

The technical evaluation was completed early this year after the six manufacturers responded to the IAF's Request for Proposal (RFP) in August 2007.

'All the trials are on a no-cost-no-commitment basis. The IAF will buy only the aircraft that meets all the parameters in terms of capabilities and cost,' a defence analyst told IANS here.