Leveling your Image.

Firstly we will level the image. For this I will use the Ruler Tool located behind the Eyedropper Tool.

A little tip before you start - Select a bright background colour like yellow first - I will tell you why in the cropping section. To select the background you………
Select an area of the image you know to be level – here I will use the line along the near side of the runway. Take your curser and position it at one side of the image and, holding your left mouse button down, go to the right edge of the image, following your ‘level’ line.

Now all you have to do is select
Image > Rotate Canvas > Arbitrary

Press OK and you will have a level image ready to be cropped.