Instructions
Destroy all of the airfighters in the area with the Batwing's main gun.
Fly to the upper left of the screen and grab the anti-anti-aircraft bombs. Use these to destroy the Joker's six anti-aircraft guns. Pick up the Lego canisters near them after they are destroyed.
Switch to the Batcopter. Fire a tow cable to catch Scarecrow. Switch over to the Batwing and fire the bombs from the Lego canister.
Move to the left or right to dodge the slow-moving bullets fired by Scarecrow. Switch to the Batcopter as soon as he is done firing and repeat the catch and bomb attack. Three bombs will destroy Scarecrow.