You can see a plane at a height of about 12.5 kilometers (km), which is equivalent to FL410 (Flight Level 410). Most planes only fly up to this altitude, making them visible with the naked eye. However, the actual resolution of your eyes may be worse due to factors like your eyesight.
Factors that can affect how high you can see a plane include:
- Plane size: Larger planes are easier to spot from a distance.
- Wingspan: A plane with a larger wingspan will appear larger in the sky.
- Weather conditions: Clear skies with minimal cloud cover provide the best visibility.
- Time of day: Seeing planes is easier during the day when the sun is out.
- Your eyesight: The acuity of your vision impacts how far you can see.
Remember, these are just general guidelines. The actual height at which you can see a plane can vary depending on several factors.
