precisely, somemore nvr say if its a new frame or old
frame.
Iran on Wednesday said it has
developed a new warplane named "Thunder," which it described as
similar to the American F-18 fighter jet.
The fighter jet is "similar to the F-18 fighter jet, but it is more
capable and has been manufactured domestically," the commander of
the Iranian army General Attollah Salehi was quoted as saying by
the state news agency IRNA.
Iranian state television reported that the jet "is able to fire
rockets and also to drop bombs and is equipped with an advanced
radar system.
"The fighter jet Saegheh (Thunder), after successful military
operations and accurately firing air-to-surface rockets in the
Zolfaghar Blow maneuvers, came into the service of the Iranian air
force today," the report said.
The air force, army and navy have been showing off their
capabilities and new hardware for the last month in the Zolfaghar
Blow war games, which come amid mounting international concern over
Tehran's nuclear programme.
The report added "the plane, which has flown dozens of experimental
flights during the last year, joined the air force with full
fighting capacity."
Salehi told IRNA the jet was "designed, remodeled, optimized and
made more capable by our engineers," and added that "no country has
aided us in its production."
[...]
I think the only thing similar is the engine intake and the twin
fins.. nothing else.. 
