If you look up in the sky on a clear day, you may see lines that either stretch the length of your horizon or are very short and emanate from a jet.
The above image was taken on Sunday, February 23, 2025 near I-64 in Beckley. Notice the jet in the sky produced a contrail (a narrow cloud of ice crystals) but it was quite short in length. The length is dictated by the relative humidity at 30,000 feet (where the jet is tracking). In this case, the air was very dry (notice the big spread between the temperature and dew point at 300 mb on the image to the right of the contrail that is circled on the image).
Compare it to the long contrails seen over Illinois this afternoon. The difference is the high atmospheric moisture content at the same level (300 mb or 30,000 feet). This allows the contrail to linger for longer before drying up, so you can see the jet’s flight across the sky without it disappearing on you! 
For more of an explanation on the contrails, see the video below.
