Welcome to the forums, chaka8!
Do these planes fly so high that they often leave contrails? Are these planes flying directly above you (90 degrees), close to the horizon (0 degrees), or halfway between the horizon and directly above (45 degrees), or somewhere between halfway and the extremes?
There is a high altitude airway J110 that extends from Philadelphia to Indianapolis. This airway is about 35 miles to the north of Baltimore so it would be between the horizon and halfway up in the sky - probably closer to the horizon. This traffic would probably be Philadelphia traffic traveling to the heartland and points beyond. There could be some traffic from Boston and some New York, but I think those planes would probably use J230 which is to the north of J110.
If you can give us more specific information about your location in Charm City, and where the traffic is in relation to you, we can better help you to identify the origin of the traffic.
You can go to http://skyvector.com, type-in BAL in the “Location Lookup” field in the upper right and [enter]. This will show you BWI on a VFR sectional chart. Then click on the “Enroute H10” link in the upper right area of the chart. This will change the chart from VFR sectional view to the High Altitude chart. Zoom out two clicks and you’ll see J110 in the upper area of the chart.