That generally means (in English,bl I hasten to add), decrying a situation that one cannot achieve oneself.
How this proverbial saying applies here is not clear.
The point was about the safety of the Tejas. Nothing has been said in that anonymous scrappy quotation that shows that the plane is unsafe. There is only a wild speculation, totally in the air, about what might happen in future.
Where does 'sour grapes' apply to this, other than to deepen your preparation for being tested on your trip on the English language? Which clearly needs further work, going by the evidence on hand.
