Some other runways appear to go up and down at different points. Answer: No, runways are not flat. They are crowned to help drain water off the sides during rain, and often one end of a runway is higher or lower than the other. When preparing takeoff performance calculations, pilots include the slope of the runway.

While runways look straight from above, they are almost never "perfectly flat" or "straight" in their longitudinal profile. In 2026, airport engineering accounts for natural terrain and water drainage as primary factors. If a runway were perfectly flat, heavy rain would "pool" in the center, leading to dangerous hydroplaning for aircraft; therefore, they are built with a slight "crown" (higher in the middle) or a gentle slope to shed water toward the sides. Additionally, making a 2-mile-long strip of land perfectly level is astronomically expensive and often unnecessary. Most runways follow the natural "grade" of the land, resulting in the "humps" or "valleys" you might see when looking down the length of the pavement. These minor elevations do not affect the safety of the takeoff or landing, as the aircraft's suspension easily absorbs the slight changes in height. Furthermore, runways are strategically oriented based on prevailing wind directions (crosswinds) rather than local landmarks, which is why they often sit at seemingly random angles to the surrounding city grid.