Several round white object sight near my flight traveling in opposite direction at a high rate of speed.

While on flight # AA6201 from Philadelphia to Greensboro.  I was in seat 10A window on the left side of the plane as we flew south.  In our ascent, I estimate maybe 4 to 6 minutes post take off, I observed the objects  I estimate our altitude was likely 4 to 5 thousand.  I know we had not been alerted to reaching 10,000 feet until many minutes later.  Looking out of the window I observe red a number of bright white round objects traveling very close to our craft moving in the opposite direction.  I was initially alarmed fearing they were dangerously close at nearly the same altitude or just below.  The plane of course was traveling at a high speed but the speed at which these objects moved by suggested to me they we moving much faster.  As a result ocould only see them for a matter of seconds.  They were bright white and as best I could tell round.  My first thought was they resembled ping pong balls or soft balls but way bigger.  Much smaller than the plane! but substantial.
Due to the speed I estimate  5 to six or more.  Each seemed to have what I can best describe as something resembling an antenna protruding from the center bottom of the object. I was hoping to learn if there were other reports from other witnesses or perhaps even the flight crew or air control.