The tower is a pretty small reference, but you have a decent horizon in view, the tops of the hangars, AND
the horizon in the attitude indicator! You know that's level. How do those look?
Do you know about the Photoshop leveling trick: Draw a line on either a good vertical or horizontal with the measure tool (nested under the eye dropper) and then Image-Rotate Canvas-Arbitrary. Click okay and your image will be rotated to dead level. I picked that one up here and am happy to return the favor.
Fine: Tax for doing wrong. Tax: Fine for doing well.