Black Triangle Sighting in Jamestown, New York on June 16th 2015 – observed bright light fly over accelerated out of sight

I was sitting on my front porch approx. 9:15 this evening. I was listening to music, watching the planes fly by, just looking at the stars. I saw a bright white light fly over (west to east). It was a triangular shape(or at least appeared to be.), and was flying about the speed of a low flying airplane, maybe a little slower. The approx. size of jupiter or maybe mercury at sunset. There were no blinking lights I could see. In a very subtle way the object changed direction to south east, (it headed approx. 45 degree angle from its original flight path). As it changed direction, it accelerated, and appeared to climb, heading toward a plane flying by. In a matter of seconds, it was gone. It appeared to climb because it got smaller in size and dimmer. This whole event lasted less than 30 seconds. I have been seeing lights like this for years...would like to know what they are!