White tic tack type object at first thought was seagull but moved to fast and then dissapeared

I was at the pool during the day and heard f15s flying above the sky so I decided to look up and see if I could see one. This was not uncommon as there was a lot of air activity due to large events north in camp david and in DC so I assumed the fighter jets were just extra security (very common to see government helicopters around the area and hear fighter jets above. When I looked up to see if I could see them, which I knew would be unlikely, my eyes caught a white object flying straight in the sky at a fast speed. I Initially thought it was a seagull and was intrigued at the sight of a seagull so far inland as it is very uncommon. After 5 seconds of observation of the object moving extremely fast in a perfect straight line, I saw a traditional large aircraft above it and was shocked at the speed difference but thought it was because the object was closer to me than the jet. Then the object continued at a rapid speed on a direct straight line and after about 15 seconds it just disappeared. It could have been less than 15 seconds but it was as if time slowed down. There were no clouds nor sun glares it just seemed to vanish. I looked around but all those at the pool were not paying attention (not a surprise as I love planes and look up whenever I hear one) I tried for days to rationalize that it was a bird but I knew deep down it wasn't in the days that followed as I monitored the speed of birds in the air and nothing met this velocity. The object was white, almost a tic-tack type shape, and was flying at extreme speeds before just disappearing