A long flight is a small badly ventilated room that runs cold, at a cabin pressure equivalent to standing at around six or seven thousand feet, with humidity closer to a desert than a bedroom. That is the environment you are dressing for. It is why the outfit that felt perfect walking through the terminal is unbearable by hour four, and why almost every experienced traveller ends up at the same formula: three layers, nothing tight at the waist, nothing you cannot sleep in.

The waistband is the single decision that matters most. You are going to be seated and slightly slumped for most of the flight, and a rigid waistband with a button and a zip will press into you the entire time. A knit or foldover waist solves it entirely. This is the reason a soft wide-leg trouser or a well-cut jogger has quietly become the standard travel bottom for people who fly a lot, and it is not a style trend so much as a comfort conclusion.

The second decision is fabric weight over fabric type. A mid-weight knit that holds its shape will look intact when you land. A very fine jersey will read crumpled after nine hours in a seat no matter what fibre it is made from.

The base layer sits against skin and its whole job is moisture. In dry cabin air you lose water constantly without noticing, and a fibre that moves moisture away rather than holding it is what stops the clammy feeling that sets in mid-flight. This is where modal, TENCEL and fine cotton earn their place, and where anything heavily synthetic does not.

The middle layer is the one you will actually be seen in, so it should be a real garment rather than sleepwear. A crewneck tee, a fine knit tank, a long-sleeve top in a fabric that does not crease: anything you would be comfortable being photographed in at baggage reclaim. Keep it plain. Print and structure both look worse after being slept in.

The outer layer is temperature control, and it needs to come on and off without a bathroom visit. An oversized cardigan, a zip hoodie or a pullover in a soft knit all work; a robe genuinely works too on an overnight flight, and is far more comfortable than the airline blanket. Choose something long enough to sit on, because the seat itself is often the coldest surface you touch.

One small thing that makes a disproportionate difference: change your base layer in the bathroom about an hour before landing. It is the cheapest way to arrive feeling like a person.

This is the part of the outfit nobody plans, and the part most likely to ruin the flight. Compression is the specific thing to think about. A firm shaping garment restricts the waist and abdomen, and on a long flight, at altitude, with intestinal gas expanding as cabin pressure drops, that is genuinely uncomfortable rather than just unflattering. Save the strong shapewear for the event at the other end.

What works instead is a light seamless brief or a soft bralette. No underwire, no hooks against a seat back, no elastic band that leaves a mark after nine hours. A wireless or lightly lined bralette is the standard choice for a reason, and plenty of people skip a bra entirely on an overnight and put one on before landing.

Avoid anything that runs a seam across a pressure point, which for most people means the hip and the mid back. Bonded edges rather than stitched hems, and a flat gusset rather than a stacked one, are the details that stop a garment printing into you over a long sit.

On compression socks: they are a real intervention rather than a wellness product, and for flights beyond about four hours they are worth wearing, particularly if you have any circulation risk. Graduated compression, put on before you board rather than mid-flight.

What should I wear on a ten-hour flight? A knit or foldover-waist bottom, a plain mid-weight top, and a soft outer layer you can remove without standing up. Add a light seamless base layer and closed shoes you can slip off.

Are leggings a good idea for flying? Yes, if they are a comfortable weight and not compressive. Very tight high-compression leggings are the ones to avoid on a long flight for the same reason as firm shapewear.

Should I wear shapewear on a plane? No. Cabin pressure drops, gas expands, and a firm compression garment turns an uncomfortable flight into a miserable one. Pack it and change on arrival.

What fabric is best for flying? A cellulose fibre such as modal, TENCEL or fine cotton next to skin, and a stable mid-weight knit on top. Skip anything that creases hard, like linen, and anything that traps moisture.

Can I wear pyjamas on a plane? A matching knit set reads as clothing and is entirely reasonable. Anything with an obvious sleep print or piping reads as pyjamas, which is fine on an overnight and less so if you are going straight to a meeting.

What about shoes? Something you can take off and get back on when your feet have swollen, which they will. Lace-up boots are the classic mistake.