You don't need Trump's word on it. I think Iran is the only country that claims the drone wasn't in international air space. So you have their word on it... good enough for you, right? As long as it's anti-American, you'll believe it, right?
I haven't been fully monitoring the coverage of this, but I haven't seen one media source, even the ones that continually hate on Trump, try to say that the drone was in Iran's air space.
I guess that's not good enough for someone like you, who obviously hates Trump more than they love their country.