That's controlled with that "fancy" black pencil. You use the Red pencil to mark an "X" on the map, and you use the black pencil to "Select" the asset to be used (the airfield in your case). "Drag" the mouse in the direction you want the search and click again, and you should see a circle draw, signifying the search area. The airfield will then "launch" a search plane to look for enemy planes and / or ships in the general direction you indicated. You don't have to click on the pencil first, but can just click on the airfield with your mouse, and that will also pick-up the pencil for you.
