This is the longest period that the Russian-made aircraft has been grounded since 2009 when its flying was suspended for nearly three weeks following an accident.
Air Force sources said the CoI is in its last stages and will come out with a report soon.
A team of 10 experts from Russia is currently in Pune, the Sukhoi-30 base, probing the crash that took place on October 14 near there with both the pilot seats ejecting without any command during landing.
As standard operating procedure, the flying of the aircraft was suspended and a CoI ordered.
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The sources said the Russian experts have claimed that the ejection of seats cannot take place automatically, a contention that is not being accepted by the Indian Air Force.
The Russian experts, along with IAF personnel, and officials from Hindustan Aeronautics Limited, besides others, are conducting a complete evaluation of the fleet of about 200 twin-engine fighter jet planes.
The aircraft will be back in operation only when the process is completed.
IAF is already down to 34 combat squadrons, as against an authorised strength of 44. Each squadron has up to 18 fighter planes.
This was the fifth accident involving a SU-30 MKI since 2009 and the fleet has at least been grounded twice earlier.