The plane uses light in the night in the sky?

Even at 10,000m, the airliners still use both "navigation" lights and "position" lights for situational awareness and visibility. The navigation lights are the steady red and green lights you may have seen on the wingtips, along with the steady white stern lights seen from behind the airplane, very similar to the red and green lights required for boats. The position lights are the high intensity white strobe lights again on the wingtips, along with a red strobe on the tail. As the planes come down, more lights will come on such as landing lights for the approach and taxilights for centerline visibility on the ground.

At 10,000 meters (and at all other altitudes), aircraft flying at night use lights that mark their position and attract attention, so that any other aircraft in the aircraft can see them. Colored position lights make it possible for other aircraft to see whether the airplane is approaching or moving away, and flashing strobe lights help to attract the attention of any other nearby aircraft.

Closer to the ground (below 3000 meters or so), aircraft often turn on powerful landing lights. These lights illuminate the runway during takeoff and landing, but they are also useful for making the aircraft more visible while it is flying. When an airplane is flying through crowded skies at low altitude, having the landing lights on helps to make sure that other aircraft nearby can see it.

Yes, plane uses light in big sky at night, no use during day, kemosabe.

Of course they use lights in the sky at night. How do you think the pilots see where they are going?

Nav lights, strobes and anti-collision (rotating beacon) are on per FAR.