Okay, at 4 months your IRN should've been well into his fledging process. Problem here is that he's getting a bit of a late start, and he's learning in a confined space. This doesn't mean that you need to clip his wings, however. You'd only be putting off the problem if your ultimate intent is for him to be able to fly well enough to negotiate all of the twists and turns involved with indoor flight.
Think of what's happening to him this way. He gets a chance once in a while to do something that he feels a powerful urge to do on an instinctive level. But combine that excitement with a lack of fundamental flight skills and you have a problem. Since he has not yet had the chance to fledge, his abilities are nowhere near the equal of his ambition. So this is where you are needed to step in and level his playing field somewhat.
My first ekkie, Bixby, had a similar experience in terms of being allowed to fledge. He was in a store until he weaned at 4 months, so he didn't get the chance to fledge as he should have. If upon bringing him home I'd let him out into the open expanse of my home, what's happening with your IRN is exactly what would've happened to Bixby.
Here's what I did:
I purchased 2 adjustable height training perches and worked with him in a small room, door closed. The limited space prevented him from slamming full speed into walls while he was learning to maneuver. (He still crashed. Just not at a speed sufficient to cause him any real harm.) And the room was cleared of as many distractions as possible. A teaching space. Nothing more.
To start, I placed the 2 training perches side by side. There was just enough space between them to allow him to comfortably step from one to the other at my prompting. (Yes, flight training and target training go hand in hand.) Each time he followed my command and went to the indicated perch, I praised him enthusiastically and gave him one of his favorite treats. Usually a sliver of almond or cashew.
Once he was reliably going back and forth on command, I began increasing the distance between the perches so that it required a bit of a stretch to make it across. And once he got confident with that distance, I widened it enough so that he had to do a little hop. And then wide enough where he had to flap his wings once or twice to cross the gap.
This incremental approach was important to begin teaching him control, to build his confidence, and to establish the targeting routine that served as the basis of his training.
Once he was confidently flying from perch to perch from across the room, I started adjusting the heights of the perches for varying difficulty levels. Also done in increments. Flying from a higher place to lower. Lower to higher. (Keep in mind that the steeper the climb or drop, the greater the difficulty. So your increments would now go in reverse. Start farther away and then work your way closer. This builds skill AND strength.) Eventually he was able to fly from down on the floor up to a fully extended perch at a nearly sheer incline!
I then stopped placing the perches directly across from each other, instead angling them so that he'd have to turn a bit in order to land. With increased confidence was a proportionally decreased tendency to panic when encountering the unexpected during flight. Why? Because he was increasingly confident of his ability to circumvent it.
Once he got to this level, I introduced him to the rest of the house. I took him on tours again and again and again, until he was intimately familiar with every window, every mirror, every hallway, every wall, and every good perching surface. ***Also important! The more landing areas you provide throughout your home, the less likely he is to crash. Why? Because he will have a landing perch mapped out in his head already. Often, it's the panic that ensues when they can't find a perch that leads to headlong rushes into the wall.
With time, Bixby became a proficient flier. He never, however, approached Jolly's level of skill. Jolly is an example of a properly fledged bird. Flying is second nature for him. But Bixby did become rather good at it. Enough so that his absolute joy for flying showed in every triumphant flourish of his tail whenever he'd pull off a particularly challenging maneuver.
It takes time and patience, but your guy can definitely learn.
Here's a really good video on indoor flight:
[ame="https://youtu.be/NzyZGdMp9kM"]Myth-busting! Parrot Training - Indoor Free Flying - DUCK!! Pet Parrot Free flight Skills - YouTube[/ame]
