Multiple objects in the sky that flash white and/or red and fly low and together, extremely visible at night.

For the past two weeks, we have been seeing a slew of objects in the sky between 18:30 and 5:30, so mainly in the dark. For all we know they might be present during the day as well. They flash white and red, some only white and there are plenty of them. At first we thought they were planes however there are far too many in a congregated space to be commercial planes. Some move quickly while some stay stagnant. They get in groups together and fly quite low in comparison to airplanes. We have seen them lower and under 1000 feet high while airplanes have passed by. They also give off a droning sound.