3 objects moving slowly emitting large dark colored exhaust/ smoke flames over 95 Baltimore

3 objects flying through sky at a slow rate of speed.  All were leaving significant smoke trails behind them.  Everyone on 95 southbound had no choice but to see them unless you were completely oblivious. 12/23/19 at approx 4:35pm I witnessed for at least 15 minutes until I was in the White Marsh area and they disappeared out of sight.  I first assumed comets but seemed to be moving much to slow and a significant exhaust or smoke flume trailed in the sky behind the objects.  I took approx. 15 photos as I drove home from work.