Timing note: Shortly after Iron Man 3

Everyone – bar statistical errors and edge cases – has dreams about falling. Not only idiots who fly non-spaceworthy hardware through holes in the sky with nuclear weapons over their shoulders – everyone.

Tony knows this because he's done the reading. Everyone has them. The scientific consensus is loose on why but it's assumed that there was some evolutionary selection advantage once upon a time. Perhaps idiot monkeys who didn't have them lacked caution and fell to their deaths too often.

In any case, the upshot is that humans are hard-wired to be afraid of falling.

And to dream about it.

Tony knows that the violent startle back into wakefulness in heart-hammering shock is called a 'hypnic jerk' and technically occurs before the onset of dreaming. The brain backfills around it, making up stories to itself.

He knows that nightmares occur in REM sleep and the thrashing, screaming, unremembered night terrors which he only hears about second-hand from Pepper occur in non-REM sleep. He knows that the horrifying helplessness of being almost awake but not yet able to move, happens in some limbo land, of chemical imbalances somewhere in between the two, called 'hypnagogia' and that the terrifying sense of imminent threat called 'hypervigilance' in that state has led to stories through the ages about succubuses and alien abductions.

People dream about aliens even without having had to face them. It's common. A neurochemical glitch that the brain puts a made-up explanation around. Demons in the middle ages. Aliens now. That his brain fills in the story with the events in New York, instead of a movie or campfire ghost story is not relevant to the biology. Everyone dreams about helplessness.

The irony is almost too much when he discovers, some way into this research, how many of the things he does to stave the nightmares off, to distract himself, to exhaust himself enough even to venture into bed, are aggravating factors. Nightmares caused by too little sleep? Well that's a toughie…

When did he become an expert in the physiology of sleep disturbances? In the nights he couldn't sleep of course. It's what he does. If you don't understand it, find out, find the research, find the evidence, find a way to fix it.

Even if the machine that's broken is you.

Routine maintenance first. Bodies are easier than brains. Rule out the straightforward physical faults.

He gives JARVIS a schedule, instructs the AI to nag him about it. He eats when he should and what he should. Swaps out the rocket-fuel-strength coffee and the booze for smoothies, making the most expensive, complicated, exotic ones he can possibly conjure up to avoid thinking about the fact it's not what he'd rather be drinking. He exercises, timetabling it carefully around the recommendations on eating and sleeping times and stopping when the plan says stop instead of upon arriving at exhaustion or injury. He meddles with his screens and holograms and lighting, following current research on triggers for melatonin production and sleeping patterns. He curfews himself from the workshop for at least an hour before his target 'bedtime'.

He does all of these things with the doggedness of chasing down an intermittent circuit fault, or clawing his way back into a fight after being smacked from the sky, but in the end he still has to do the hardest thing.

He has to lay down and shut his eyes.

Has to do it even knowing the nightmares will come. Has to lie in the dark, counting breaths and trying not to think, like a prisoner waiting for his captor. Has to lay down again after each one, instead of fleeing to his distractions. Has to lie there, watching the physical signs of panic slowly fade, counting too-fast breaths and heartbeats and waiting. Has to accept that this might happen 5 or 6 times a night. Has to accept that sleep – though he is getting more sleep overall – will be this way for a while, in dribs and drabs and snatches.

He tries to persuade Pepper that he should sleep alone. He fails entirely but he hates waking her. The first few nights he only succeeds in staying put maybe half of the times after waking, and of actually falling back to sleep less than a third of those. He monitors both ratios, treats them as data-points for this fault fixing exercise. They improve. Slowly.

When he still looks like hell in the mornings, or Pepper finds him already in the workshop after all, or he finds her sleeping downstairs, driven out by his tossing and turning, they both shrug it off. She knows he's trying she tells him. It'll get better she tells him, and she curls her fingers in his hair to draw his head against her shoulder, makes coffee – morning coffee is still allowed – and helps him hide the dark circles under his eyes from any press they have to deal with that day.

After the first night that he sleeps through without waking they celebrate by going out for breakfast and eating an unreasonable amount of sweet, sticky pancakes between them. Progress isn't steady though. He continues to monitor his sleep patterns like suspect engine Ts & Ps, or a Mean Time Between Failures metric for his own head, and it's a scatter-graph, a trend-line, not a linear progression. The trend is to improvement but there are outliers.

This is an outlier.

He's dreaming, and he knows he is, because it wasn't like this, not quite. In the dream he's conscious all the way to the ground. In the dream no one catches him. In the dream his suit is, in some dream-logic way, not the suit he wore then but his most recent one and all his clever tweaks and fixes make it worse. Micro-repeaters under his skin. Tactile feedback he'd thought would help with the responsiveness of the armour. That would eliminate that split second lag between intention and reaction. It does, and in a fight it's fantastic.

And now it's terrifying.

He tumbles through the air and the sickening giddy fear isn't only his inner ear protesting. He can feel it through the suit as well. Feel it under his skin. Every gyro toppled, horizon lock lost, he knows it before the HUD tells him so, and even after the HUD loses power and shuts down. He doesn't know which way is up so even if he redeployed what little reserve power remains to the flight systems he might only be driving himself towards the ground faster.

He can feel the air pulling and pushing at the control surfaces from all the wrong angles, turbulent and useless.

He can feel the power loss, the flickering, failing repulsors, as a weakness in his own limbs. It's not real, the waking part of him knows. It's his brain's own personal take on the 'legs too heavy too run' dream that everyone has. It means his brain has correctly prevented his body from really flailing his limbs about as he can't stop himself doing in the terrifying fall that still has him in the dream.

It doesn't help to know this.

He knows what comes next, knows he'll hit the ground, knows it will hurt, knows the research on the experience of pain in dreams in incomplete and that he doesn't care because he knows it damn well hurts. Knows the feeling of broken bones, crushed lungs, and he wants to wake up now because he can't breathe, even before he hits the ground he can't breathe and he wants to wake up, he really wants to and he can't and he can't breathe.

Abruptly, he is awake and he's woken Pepper too because she's telling him to breathe more slowly and that's a good joke because he can't breathe at all. Until something lets go, and she's right after all. He's breathing – if hyperventilating can be called breathing – but this at least he's learned to fix. He counts, stubbornly, forcing his unruly breath to order, and Pepper murmurs reassurances that he doesn't really hear, and it passes. He thinks about getting up. He can't face that again, not tonight but he's too wrung out to move.

He's exhausted and frustrated and irrationally angry, because it isn't fair. He's done everything he should, everything that's supposed to help, and he misses his stupidly over-priced after-dinner coffee to a ridiculous degree and he hates staying in bed when he's awake and he's done all the things anyway and he really damn well didn't deserve this one.

He opens his mouth to protest to Pepper about the general unjust nature of the universe since the first flush of anger has already faded and perhaps he can still make light of it. Except it turns out his breathing isn't entirely under control after all, with the result that the first sound that comes out of his mouth is humiliatingly close to a sob instead of a word.

He changes his mind about talking, listens to Pepper instead, still telling him he's okay, he's safe, he's here. He thinks she's still talking when he falls back to sleep.

In the morning he gives in and reads the psychology as well as the physiology and by the afternoon is newly expert in all the research published on 'image rehearsal therapy' for the treatment of nightmares. He still thinks it sounds like a fancy way of saying 'making up a better ending' but the effect sizes in the studies are statistically valid enough to make him try it. He follows the method. Writes down the specifics of the nightmare is such detail that he gives himself two nights of total sleeplessness in the process, then adds a plausible alternative and practises visualising it. Adds the mental rehearsal of the alternative – the 'good ending – to his night time routine. Every night. Whether he wants to think about the dreams or not – and he doesn't, he really doesn't – but he does it anyway.

It's too soon to tell if it's any help but he's Tony Stark and that means he can't stop himself trying to engineer his imagined solution in the real world.

He tells Pepper this time. About a new suit. Promises it's a project not a hiding place. Refuses to let it break his self-imposed curfew. She doesn't try to dissuade him, and he's glad and a little ashamed that he doesn't know whether or not he'd have let her if she had.

He paces in circles in the workshop calling out idea to JARVIS who projects the list into the air around him so Tony can wander amid the holograms, sliding them around with his hands as he mulls over priorities, grouping and sorting them.

He needs to not fall. So he needs more power. Or more efficient power consumption. Maybe an entirely independent power source altogether. More accurate warning of pending power loss. More reserve. Something kept back for last-ditch impact protection? Faster failover from primary to reserve. Fewer single points of failure. An alternate power source for just the gyros and flight systems maybe. A low power mode for the HUD – he flicks his fingers to fork that item and starts a new list of just the bare minimum information he'd want on that and calls up another display to keep a running total of power demands for the various systems as he swaps options in and out.

He calls another display up for the physical suit design which he runs his fingers over, reshaping and pulling out details, proportions, sizes, looking for space and weight saving to fit an additional reactor. He twirls the image and zooms it in, stares at the flight surfaces until he's no longer really seeing them and thinks about controllability, about asymmetrical power loss, lift coefficients and vectored thrust. He throws up another comparison chart and plays with the numbers before sweeping his arm to drop the whole lot onto a work-surface to draw some designs later.

What else? For a moment he lets the nightmare back into the edges of his attention. Cold space. He needs better thermal protection. Faster suit-up if that means extra layers instead of new materials, so he doesn't lose any time in preparation. He sets JARVIS to researching materials and another list joins the others floating around him.

He thinks about pressurisation. He could seal the suit, as against water, but the air becomes terribly finite that way. Even the thought of it makes his breath hitch but any way he can immediately imagine of carrying oxygen in a fight just seems like an invitation to an almighty kaboom, and for a moment he's seized by the mental image of flames flickering around the suit, can almost feel the heat, the too hot air in his lungs. He can see the explosion that engulfs the alien fleet as he falls away from it, but he's not falling fast enough and it will take him too and he'll burn...

He staggers out of the glittering circle of holograms to lean against the wall, gasping. This time it's JARVIS who calls out to him to breathe, reminds him where he is. Tony breathes as instructed until it passes. He looks at the time. It's half an hour earlier than he'd normally abandon the 'shop but he thinks he's done here for now. He tells JARVIS to save it all and heads out. Pepper will be pleased, anyway. He doesn't volunteer a reason for his early finish and she doesn't ask.

They watch a movie which she falls asleep before the end of – he knows he's been ruining her sleep too – and he carries her to bed. He falls asleep with his arms around her but his dreams are filled with heat and flames. Explosions, and Killian leaning over him, smiling, burning through the immobilised armour, and telling him to close his eyes. To die quietly, blindly, helplessly.

Tony's eyes fly open instead and he comes to, rigid on his back and gasping.

That was a new one. Not unexpected perhaps, but new.

He's still got one arm trapped under Pepper's shoulder but somehow he hasn't woken her. He almost wants to and he cringes at the selfish impulse. He wants her reassurance, but he can't dump this one on her. Extremis he could deal with but he knows she has her own nightmares about Killian and about burning. He keeps quiet, drags his free hand over his face and goes limp where he is. Waits for sleep to return.

Thermal conductivity – he adds to his list the next day. Less of.

He narrows down the choices. Chooses between compromises. Finalises a design. Resists the urge to turn one into twenty to embody every possible variation of his decision-making. The number of holograms floating around him reduce as he dims and then swipes away list after list of to-dos until the only thing left is a life sized image of the suit itself and a single outline of specs.

He tells JARVIS to begin fabrication.

His dreams that night are restless, filled with second-guessed design decisions and numbers he'd stared at so long they seem imprinted on the back of his eyes, but there are no nightmares. He sleeps late, woken by Pepper leaving for the office. She tells him to be careful and he resists the urge to joke about it and instead says he will.

JARVIS has prepared a test plan and safety brief for the new suit and there's audible, almost human surprise in his voice when Tony asks to see them. They're comprehensive but Tony still adds to them – there's things he wants to be certain of. He doesn't want to fall.

Eventually he's ready and he lifts his arms away from his body and lets the suit enclose him. He times it in his head, monitoring vulnerable points during the procedure, calls a note or two to JARVIS of his observations.

The HUD comes live and he runs the test procedures from the plan. Controls, power, data, feedback. He cycles through the redundant systems and brings the power up gradually. When it reaches a level just sufficient to drift his feet off the floor he feels a smile start to spread across his face.

He contains himself long enough to step through JARVIS' initial power and stability checks before giving into the temptation to just hit the juice and take off into the open sky. He's promised – promised he'll be careful and so he maintains straight line flight but there's a glorious amount of excess power and he accelerates even in the vertical and he'll have to talk to Pepper, really explain, because he can't give this up and he can't make himself use it just for kicks and giggles, not if he can use it at all. Not and maintain any illusion that he's even a half-way decent human being.

JARVIS calls 10,000 feet and it's their selected altitude for testing so Tony agrees the reduced power setting and comes to a hover, balancing in the air with the slightest of wobbles – he's a shade out of practice. He frowns, accelerates again, stops, repeats the manoeuvre until he's happy with it. JARVIS makes no comment other than to project the planned test programme onto the HUD.

Tony smiles again at the first thing on the list – he's more than happy with full power performance and not even the prospect of the items further down the list which he's trying not to think too hard about now he's in the air, can damp his enthusiasm for the first set of handling trials. They're too perfect an excuse to twist and turn around the sky until JARVIS mildly interrupts to ask if the general handling can be marked satisfactory.

Tony's tempted to answer with a no, just for an excuse to continue, but instead allows that they are. He's not nearly so enthused about the next set of tests. The failover power trials had been perfectly reliable on the ground but this was about measuring the height loss and delay in the air, and the first attempt drops his stomach through his throat as he falls for just a second. Less than a second probably but enough to leave him shaking – the adrenaline of a fight would make this a hundred times easier. But he's promised he'll be careful so he tests it, systematically. He does it again and again, from the hover, from level flight, from turning flight. Makes himself get used to it. It works. It flicks over every time and yes there's a hairy moment but it does work. The system is solid. He takes the automatic system out of the loop, cuts primary and calls for secondary a second later, then two seconds, then three, then ten. It works. It's stable.

He comes to a halt in the air again, schooling his breath back to a slow enough pace to be able to discuss the results with JARVIS without panting, and to recap the next set of manoeuvres.

Cutting one repulsor at a time he practises partial power recoveries, recovering his balance in the air, juggling power and angles. He learned this the hard way and he's good at it, but the new power settings still mean he's all over the sky at first. It ought to feel like falling, but something about the physical challenge, the concentration needed or just the adrenaline belatedly cutting in means he finds himself grinning. A teeth-clenched, furious, elated grin that he knows probably looks entirely manic. He tells JARVIS to randomise the cuts and deliberately pitches himself over in the air, tumbling and recovering, again and again. He's so focussed he can almost see the physics of it overlaid on the reality around him like one of his holograms. Can almost see the thrust lines, the laminar flows breaking to turbulence and reattaching.

When he comes to a stop he's dizzy, and breathless again, but with exertion not traitorous anxiety and there's something cleansing about it. He takes deep breaths of the high, clear air. He's disoriented and it takes him a moment of scanning the city below before he can pick out the tower and swing himself round towards it. He's pleased with the suit's performance, but he's tired and thinks that he might actually want to get some sleep. He tells JARVIS to mark the power loss and failover procedures successful and flies towards home.

He can't remember the last time he slept during the day, but Pepper finds him sprawled out on a couch when she returns for lunch, with debriefs and test results still projected into the air around him. Her hand brushes his shoulder and he drifts awake, warm and sleepy in the afternoon sunlight.

She tells him he looks good and he laughs because he knows he looks wrecked, bleary-eyed, un-showered, and rumpled from sleeping in the same clothes he'd worn under the armour. But he knows what she means and it's not his state of grooming.

He knows he can't engineer his way out of nightmares. Not entirely. But neither is he helpless against them. Neither is he alone.

And he's not falling any more.

Note: Thoughts and feedback as always welcomed. This got longer than I expected and I almost rewrote the 'daytime' chunks to be more narrative+dialogue instead of the Tony-internal-monologue they began as. I'm still in two minds if that would have been better. Is it too long for this stream-of-conciousness style?

There's a sort of side-piece to this over on Deviant Art (I'd link but FFnet seems to object to that! Username is the same) Part of the idea for this story came out of a flying incident I had a while ago and I gave myself a minor dose of the abdabs converting it into a fic!