WE <3

I think I saw something unusual however I’m not familiar with air travel, perhaps someone could tell me what it was.

In 2008, climbing to altitude leaving Chicago for London, we rose above the clouds and leveled out, and I saw many airliners doing the same, leaving white jet trails . Then I noticed a large fat cigar shape protruding from the clouds almost straight up, it very very slowly emerged, no wings, no windows, nothing like the slender jets speeding away, then before the bottom end cleared the clouds, it slowly slowly plopped over flat, like a boat in the water and sunk back into the clouds, it took about 5 minutes, and it reminded me of a breaching whale flopping over, also of a blimp without any passenger gondola, however I never saw a blimp maneuver like that. I thought, for how far off the other jets were, this craft was either very very large and I was not judging the distance correctly, or it was uncomfortably close. I was going to ask what it was, but other travelers noticed it and did not seem to think it unusual. I know the attendant saw it, but she kept speeding through her tasks, even though I think I saw her start and wondered if they were trained not to notice anything passengers might get upset by.