Dark, cigar shaped object flew in and out of a cloud before changing directions, speeding up and vanishing into blue sky.

Midday, amidst a mostly clear blue sky, a singular fast growing cloud overhead caught my attention. While watching it grow, a dark cigar shaped object immediately appeared below it, which I thought was a high flying bird. It swooped through the sky much like a bird in a high air current until it disappeared into the cloud. When it reappeared, it was mostly still, moving only slightly for quite a while. This is when I realized it was clearly not a bird. A few seconds later it changed directions, heading in a straight line to the east. It immediately sped up and then disappeared into the blue sky. About 5 seconds later, a white fighter jet suddenly appeared in the same area of blue sky the cigar shaped object had disappeared in. The jet was heading north. The jet noise was immediately audible. If they were at the same altitude, the cigar shaped object would have been almost twice as large as the length of the jet.