Vivid Cross in the sky for 5 -10 seconds, then gone

I was only 6 or 7 years old and the neighbors across the street had a ranch with many acres. I spent the night there with the girl, she had 2 older brothers and they had seen it before. We lived near the air port (Dulles), and I even said, It's a reflection, just like the Brady Bunch, but we all ran outside, and it was still there. By the time the parents got outside, it was gone, and they thought we were just imagining things or seeing things from the airport. I lived by the runway for 25 years, and I will still say to this day, I never saw anything like I saw that night.