Bright flashing light through the trees. Timing it has shown it goes off every 39-41 seconds. Airplanes also heard above

Standing in the driveway with my girlfriend talking and smoking a cigarette when we look up through the tree line and see a bright flash of light.  Just thinking it was lightning we ignored it, until I saw it 3 more times.  
We stayed outside for another hour until we went to get her mom.  When we told her about it and she saw it she tried to pass it off as lightning but there are no clouds in the sky.
She then told us that she saw the light when she was dropping s friend off 2 hours earlier. The light is in the same spot not moving just continuesly flashing consistently at 39-41 seconds per flash.  
We also noticed that there was an abnormal number of planes out.  We started counting and counted 6 planes in 5 minutes all in the direction of the object and one flying low directly overhead.