On SufficientVelocity, there is a fic called Harry Potter and the Shipgirls, a Kancolle/Harry Potter Xover. I'm crossposting what snippets I post there. I advise you read at least some of that fic, to understand some of what is going on here, though I will included glossaries when necessary.
I've posted a few snippets of my own there, but they're probably not Potter-y enough that they can be posted here.
This is a concept I've been thinking of on and off for a couple of years now, but I was always concerned I'd do it wrong. Let's just say, we're treading on ice here.
Blood Week. August, 2005.
That's when the Abyssals attacked. They wrought chaos upon the world, ravaging navies and civil fleets alike. Their campaign stretched inland as well, many cities flattened by the onslaught.
It was only through the appearance of the shipgirls, that the Abyssal's could be turned back.
What few knew at the time, was that the Abyssals had been probing human defenses for years. And that one fateful day, they changed history before they intended.
Somewhere over the United States Eastern Seaboard, Years before Blood Week...
The sun shone brightly, its rays unimpeded by cloud. The temperature at ground level was warm.
There was nothing remarkable about this day. It was just nice and sunny.
However, about thirty thousand feet above the ground, a flight of three aircraft droned through the frigid atmosphere. The planes resembled P-51 Mustangs, but there was a wrongness to them. They were made of sheer black metal, unnatural beast-like pilots at the controls. Their Merlin engines didn't sing majestically, instead they emitted a hideous, guttural roar.
Two raid flights soared through the skies over the Eastern continental United States. Not one human on Earth knew they were up here. Somehow, even the most powerful RADAR systems could not detect them. The flight could operate with impunity, but not for long. These were the first aircraft the Abyssal's had sent over land, in a test of their own capabilities, and the defenses of the humans.
The mission they had was simple, but would provide vital data for the Abyssal's inevitable assault on the humans.
The flight had found a suitable target: an airliner, an aircraft that made the corrupted Mustangs look like toys. It may have been huge, but it was utterly defenseless. Its gleaming silver skin was simple aluminium, not a single plate of armour to be found. It flew at least five thousand feet below them, on a rough heading towards the coast.
This aircraft had been chosen for its erratic flight path. The Abyssal Mustangs had no access to human radio channels, but it was a safe bet that the silver behemoth was in distress, unable to stay in a straight line, losing height. If it crashed, it would be assumed it was due to whatever issue was afflicting it.
The lead Abyssal pilot turned to his wing-men, silently gesturing his attack orders, before sending his aircraft into a dive. His wing-men followed, the roar of their engines heard only by birds and a few scattered humans.
They only saw the airliner as it passed overhead, and assumed that was what they heard.
The Abyssal Mustangs continued their death defying dive, a maneuver that would have made an ordinary Mustang break apart under the speed and stress. Less than a thousand feet from the target, the three fighters opened fire with their wing mounted 50 cals.
Eighteen machine guns thundered, streaming a hail of black bullets into the hapless airliner, piercing its silver skin with ease. As the fighters raced past, the airliners stricken fuel tanks ignited, a ball of flame erupting from the planes belly and leaving thick black smoke in its wake.
With a slight wobble, the doomed aircraft keeled over and descended out of control, breaking up into several pieces, a large majority of the wreckage striking a farmhouse far below.
"̧̫͕̟̖̝͔T̖̙͙͖͝a̧̮̯r̢̝̙̳̘̘ͅͅg̺̹̞͈̝̣e͍͉̤͔̕t͇̝̞ ̲̣̀D̵͉͔̤͚̻̗͙e͍̤̝st̰̞̩̼̼̱r̲̞̠͓̼̼̘͢ò͇̲̼̯y͖̮͙̟̤e͇̱̱d̡̝̙̟̘"͍
.
The Abyssal flight leader reported to its control. A similar report came in from the second flight. Both flights had each succeeded in downing a human airliner. Columns of smoke rose from the crash sites, sullying the once cloudless day.
"̺͓̲͍Wa̡͈̝r̻n͇̠̙̱̦͟ͅͅìǹ͕g̟͓̲̣͍̝͝ͅ! ͔̲̖H͎͓̘̝̱͟u̻̜̩͠ma̯̮̪͎ͅͅn͚̮̘̝͈ ͙͖̳̠̦̼f̮̪͍i̫͕̬g͓̜̬͜h̡͉̱͉̣ț̷͔͙é̬͓̤̪̰ŕ̳̬͖s̟͚̦̳͚͙͈͜ ̪̪͙̘d͢e̷͙̙̼͈͈̹ͅt̼͎̼̪̘̳͔͡e̡̜c̶͚̥ṭ͚̪̜̘ͅè̥̣̥̜͙͍d̼̥͙͝ ͏͙̯̫͉ḁ̟p̛̫͎p̮͙r̸̰̤̰o̻͕a̘͉̥̜͈͎̗ch̭̖̖̥͙͖̲̀i̷̜n͕͙͙̺͟g̟͖̞͉ s̲̼̩̭̼̫̕e͏̹̘l̥f͏̲͎̟̪͇ ̦͍̣p̵͔͔os̺̦͖͇̩̞̜i̵̘̼͎̳̹̫t͘i̠̦͇̫͍on̤̲͖͙̱̦.͈̳͔̲̀ ̟͈̲̱̰̀R͍̬̱̙̥ͅͅe͓̹̜̳͙̖ṱ̜̫͙̺̥uŗ̣̤n̵̲̞̙̭͔ͅ ̶̙̲̦̣̦t͈̘̼̫͠o̻͎̰͍̰̞̙͟ ̴̙̻̤b̠̕ͅa̮͝ͅs̀e͡ ̦̼̻͡a̗ṭ̰͉̰̯̹͎ ͎̭̻͖b̖̼̺ęs̘̼̫̭̠̠͈ț͍̱̼ ͕͕͍s̯̳̱͍̗͙͢p͇ẹ̡̟̗̼̤̣ed̴͕̦̯.̫̖̯͓"̣
.
The bestial Abyssal pilot turned its head to the West. In the distance, it could see three human jets rapidly approaching. Had the attack been detected? Had the airliner relayed a distress call? There was one way to find out.
With a wordless order, the flight of Abyssal Mustangs fled the scene at a speed unthinkable for its normal human variant. In no time, there was no trace of them over the crash site.
The human jets did not give chase. They had not detected the Abyssal craft. Instead they hung around the crash site, seemingly investigating.
This information was sent to control. It would prove to be crucial for their plans.