Grainy web images of what is believed to be a new Chinese fighter jet create a stir . Known as the J-20 , stealth fighter is n't supposed to be operational until at least 2017 . A Pentagon spokesman says the United States is aware of situation , but it is n't fretful about it . Stealth jets , such as the United States ' F-22 , are designed to evade detection by radar and anti-aircraft defenses . Comment:
Grainy web images of what is believed to be a new Chinese fighter jet create a stir . Known as the J-20 , stealth fighter is n't supposed to be operational until at least 2017 . A Pentagon spokesman says the United States is aware of situation , but it is n't fretful about it . Comment: