Well I mean without going to any form of "official/unofficial" sources, Yes.
He was on a plane with a load of gas that would kill him, 17000+ feet up (5000+ metres), without a parachute and either land or water below him, either way from that height they're effectively the same.
The explosion from the plane alone looked big enough to decimate him. Followed by the impact from 17000 feet of free-fall. He's dead.
Now on to the novelisation. This is as canon as you want it to be. But here it goes.
With numbed fingers he took his pistol from its holster and pointed it at the bombs. He chuckled to himself. He wasn’t afraid. But he was wistful. He wanted to show Diana the beautiful parts of this world. To share it with her. Newspapers and breakfasts. It was not to be.
It was not to be.
Still, he couldn’t stop smiling when he thought of her, and of what he was doing, and what this would mean for the world: Peace.
The world was going gray. He was getting loopy. He closed his eyes and pulled the trigger and as he did he said…
This seems to suggest he shot at bombs, igniting and killing him most likely. The way he acted seems to suggest that he was about to die.
She exploded, a half-God bent on vengeance, and in one savage push, she freed herself from the tire tread wrapped around her.
Then the image of Steve’s face filled her mind. Their last moment together...
This seems to further suggest he's dead and gone forever.
That being said, it's a comic book film, they'll bring back whoever they want.