[quote=@Burthstone]
<Snipped quote by Silver Fox>

That was Dragon Force, not another element he used.
[/quote]

That and it was only temporary, the next time we saw go into Dragon Force was in the Tenrou Arc. This took place several arcs after Natsu first used it, I'm actually not sure if Natsu knows how to voluntarily activate. Unlike Sting and Rouge who can activate theirs at anytime.