Tata Group chairman emeritus Ratan Tata has lashed out at old Indian carriers' bid to ensure that the 5/20 rule - which makes it mandatory for desi airlines to be five year old and have a fleet of at least 20 planes to go overseas - is not done away with. NEW DELHI: Tata Group chairman emeritus Ratan Tata has lashed out at old Indian carriers' bid to ensure that the 5/20 rule - which makes it mandatory for desi airlines to be five year old and have a fleet of at least 20 planes to go overseas - is not done away with.