The best strategy for Airfield Chase level 9-11 is to fire Big Brother slightly downward and through the sand blocks under the left structure. If done correctly, the whole left side should be destroyed. Launch the White bird far, dropping the bomb just right of the gas can. The explosion should clear the level. The score in the video below is 81,870.
Note! With the v1.3.1 update Rovio flip-flopped level 9-10 and 9-11, hence why the level number in the video below shows “9-10”. The walkthrough is correct though and the leaderboard entries have all been switched to reflect this change.