Sure it’s simple to tell when you’re flying over the clouds, but what about anticipating whether you’ll be flying into the clouds if you maintain your current altitude? This is a pretty important concept for any VFR pilot.

Using the horizon as a guide you can usually estimate the cloud level relative to your altitude. Below is a view of the Catskill Mountains in NY. If I was flying toward the mountains I would be a little concerned with my flight level. You can see that most of the clouds appear to be above the horizon and if I got closer they would most likely be above me but not by much. However there’s at least one cloud that is breaching the horizon line and would probably be at or below my current altitude.

I was recently reminded of this tip when I was about 700′ over Boston. Since 700′ over a congested area is a clear violation of 14 CFR 91.119 I must have been in a building.

This is the view from the Skywalk Observatory on the 50th floor of the Prudential tower looking down KBOS runway 9 in the distance. After watching planes land for a while, I noticed a cool effect on the on Hancock Building. It looked like I could see though the building to the horizon on the other side. As you can see it’s a CAVU day and this is actually the reflection of the horizon behind me.

To bring this back to the cloud topic, you can see in this image that roughly 10 floors of the Hancock building are above the horizon and higher than my current level of floor 50. Well guess what, the Hancock has 60 floors.

So if you see a cloud, aircraft, building, or anything else on the horizon line in front of you, you might want to consider an alternative route.