The trail is said to have cut a swathe through the clouds, a "clear path" through which they could "see the blue sky" . This sort of effect does occur and is called a distrail (opposite of a contrail) . But what puzzles me about this is that the weather description says the sky was clear apart from only scattered cumulus at 8000 - 10,000ft. And the witness reports refer to these clouds as the clouds concerned. But true cumulus clouds are not thin sheets, they are deep volumes. Yet the reports say that the cloud appeared to be cut through by the trail. How does a narrow "sharp edged" gap get cut through a deep cumulus so that the eye (and the camera?) can see clear through to the other side?
This means cutting a deep slice, a deep vertical-sided canyon if you like, right through the bulk of the cloud, cutting it in half. This is a very peculiar thing that seems hard to understand as any kind of physical aerodynamic or other effect due to a passing object. And in any case, to see up through this narrow chasm all the way to the sky beyond, the witness would have to be very fortuitously positioned in relation to the chasm, and if the witness is looking at a low elevation through a car windscreen the chasm would have to be cut through the cloud at a strangely oblique angle (not vertically, as would be more "natural" in any plausible-sounding physical theory).
On the other hand, a gap more like a thin line, that would be visible over a wide range of angles, is possible if a distrail is caused in a thin cloud sheet.. Yet there was no thin cloud reported. But is that reliable?
It isn't certain where the cloud info comes from. The 8000 - 10,000ft scattered cloud is given as an approximate guess ("I'd say . . ." writes witness John Woodruff) in the observer accounts, so they may actually be the source. The Incident Checklists under "weather conditions" appear to quote the witnesses. I can find no other data given that would suggest proper weather reports were obtained.
So maybe the cloud was not true cumulus but instead a patchy layer of thin stratiform cloud like cirrus, for example . That would more plausibly allow the object to have cloven the cloud in the way described.
Then there's another possibility: could the "gap" actually have been a shadow cast from above onto a layer of thin cloud by a dense contrail or smoke trail? The object did leave a trail of its own, distinct from the apparent gap in the cloud, and this trail is said to have been visible "right through the cloud" and described as "dark blue black". A shadow of a dense trail cast on the thin cloud could appear much like a gap because the thin cloud would not have significant opacity to transmission of skylight, rather its apparent density would be due to brightly scattering sunlight, like full-beam headlamps in fog dip or extinguish the lights and you can see though it. Similarly where the trail shadows the cloud the deep blue of the sky above would become much more visible again.
In that case any kind of object that leaves a dense smoky trail could be the cause, but if the trail is truly horizontal above the horizontal cloud layer then a meteor trail would seem unlikely, even if the cloud was really high cirrus. A smoky jet or missile might do it. But of course this comes up against the claim by one of the witnesses that he actually saw a translucent disc making the trail.
It's a pity that the making of the trail could not have been photographed as it happened. But it would at least be helpful to have good copies of the photos that were made. Do we know where these are?
One other point to note: Two of the witnesses describe the apparent gap through the cloud in interesting ways one says the edges appeared "feathered" and compares them to "cutting a weld in half" (referring I suppose to chevron-like ripples along the length of the weld); the other says it was like "a pebble leaving a ring in the pond", presumably implying that the edges looked rippled. This interesting structure could be said to argue against the shadow-on-thin-cloud theory (on the other hand the structure could possibly belong to the trail above)