My air cushion went rock hard on a flight last year, do you actually have to let it down once you're up there?

Odd one but it's been bugging me since last summer. Four hour flight, sat on my usual air cushion like I do every day, and about an hour in it felt completely different, hard as a board, like I was perched on top of it rather than in it. I put it down to a bad seat and a bad day. Got home and it was fine again.

Now I've got a 12 hour flight booked for November and I'm not sure I can live with 12 hours of THAT. Somebody at my wheelchair clinic muttered something about altitude and air cushions but then the appointment moved on and I didn't ask.

So, is this a known thing? Do people let air out once they're up there? And if so how do you know how much, because I'm not exactly going to get a hand under myself in a middle seat with a stranger either side. Also slightly worried that if I fiddle with it I'll get it wrong and end up sat on the plastic base, which is the one thing I've been told never to do.

Not a cushion user myself but my sister is and she says exactly this happens, every flight, and she and her husband have a whole little routine for it. He does the checking when the seatbelt sign goes off. So you're not imagining it Derek.

Same physics as my POC bag going tight and the crisp packets blowing up, the cabin pressure drops so anything sealed with air in it gets bigger. I was told years ago that cabin altitude is somewhere around 2,000 metres even though the plane's far higher, which is why it's not dramatic but it's definitely there.

What I'd say from a lot of long flights with kit: whatever you do, sort it out on the ground first. Practise the hand under the seat bones check at home until you can do it without looking, because on the plane you'll be doing it half asleep with an elbow in your ribs. Aisle seat helps, and on a long flight I'd want an aisle seat anyway for the toilet trips.

Derek C. said:

end up sat on the plastic base, which is the one thing I've been told never to do

Derek, the short answer is yes, this is a known effect and the cushion manufacturers describe it in their own instructions, so your clinic was right to mention it and worth going back to. As the cabin climbs to its cruising pressure, which on most aircraft is the equivalent of roughly 1,800 to 2,400 metres of altitude, the air sealed inside the cushion expands. The cushion firms up and lifts you out of it, and the immersion that spreads your weight across the cells is what you lose. On descent the reverse happens and it softens again. That matches exactly what you felt an hour in, and 12 hours of it is not something I would want you to sit through.

What people do about it is release a small amount of air once the aircraft is at cruise and the seatbelt sign is off, check the setting the way they were taught, and add the air back before descent, which is why it is worth setting an alarm for about 40 minutes before landing. The setting itself is the part I cannot give you from here, because it depends on your cushion model, your weight distribution and your skin history. The general check most people are taught is a hand slid under the seat bones with about a finger's depth of clearance to the base, but your own seating clinic set your cushion for you and they should confirm the check and the target for your flight, not a forum. Bottoming out on the base is worse than sitting on it slightly too firm, so if you are ever unsure in the air, leave it firmer and do your pressure lifts more often.

Two practical points on top of Sue's, which are good. First, the cushion goes into the cabin with you and never into the hold; if it is delayed or damaged you have nothing to sit on at the far end. Second, the altitude effect is one reason the whole flight needs a plan rather than just the transfer, and Marnie has set out what that plan looks like in long-haul flights in a wheelchair, including the pressure lift timing, fluids and the toilet question. What to carry on and how to protect the chair is in flying with a wheelchair.

Where I stop: how often to do your pressure lifts, what compression or clot prevention is right for a 12 hour sector, and whether your skin is currently in a state to sit that long at all are questions for your own therapist and doctor, and a 12 hour flight is a good reason to book that conversation now rather than in October.

Nothing to add on cushions but on the middle seat point, ask for a bulkhead or an aisle when you book the assistance, not at check-in. I've had far more luck with seat requests logged with the assistance booking than with anything I asked for at the desk.

Update. Managed to get back to the seating clinic this week, told them about the flight, and they did the whole thing properly: showed me the check, wrote the target down for me, and had me practise it sat in the chair with my eyes shut which felt daft but I can now do it without looking. They also told me to let a bit out and re-check after 20 minutes rather than doing it all in one go, which I'd not have thought of.

Asked for an aisle seat with the assistance booking as Fran said and it's confirmed. Alarm set for 40 minutes before landing already, which is possibly a bit keen given it's November. Thanks all, this thread turned a thing I was dreading into a thing I've got a routine for.