Why should all the MKIs selected for upgradation be grounded ? I was under the impression that most technologies required for the upgrade are either being developed or are under testing post which they'd be installed on board 2-3 such FAs & tested.Neither is easier because of the number of unknowns.
Also the entire reason why Super Sukhoi is stretching this long is because the aircraft will essentially be grounded until the upgrade is complete and IAF does not have the luxury of grounding 100s of aircraft that form its mainstay.
Even the F-16 PoBiT upgrade program is meant to run for a period of 6 years.
Once the entire upgrade is certified as FOC , it's replicated on the other MKIs. Reportedly the entire process is divided into 2 phases of 8 years each wherein 8 years would be for development testing & certification of those technologies & another 8 years for installation of them on board ~ 88 nos MKIs followed by certification.










