Are sweatpants frowned upon on flights?

I haven't traveled to east Asia or East Europe before but that is a very long flight, I don't think jeans are comfortable at all for that many hours. I have though traveled to central Europe several times and have never worn anything other than sweatpants and nothing has happened, even though they usually don't trust travelers from my country easily. It could be a cultural preconception since you observed that others were wearing jeans. But for the border police, it should be fine as long as you have all supporting documents.

It all depends on where you are from. Being from east Europe myself - we'd put our most official nice clothes for even going to the store literally 2 steps from the house.

Having lived in the UK for 8 years now, I've realized how stupid this is, and more importantly, no one cares how you look, in a setting where that is not the most important thing. I'd just do what the locals do, and go to the store in literally any clothing.

Soon after my newfound wisdom, I applied it to my flights. I'd used to put jeans or proper pants, and a dress shirt (my most pretty and official clothes I owned basically) even when it was very hot. More recently I'd figure, just as I don't give a crap, no one else does too, or even if they do I'll never see them again, so I'd fly in short shorts or as you asked - sweatpants, I'd make myself comfortable. Especially after flying so much, and having seen everything (grown ass people flying in their PJs, or a tank top and the shortest shorts, sleeping on the terminal, etc.) it's better to make this process as comfortable to you as possible, and not bow to some imaginary society constraints in your parents heads.

P.S. You need to see some UK Stag doers and the way they fly to really understand now much people don't give a crap.

I traveled for Work a lot! I mean a lot. I used to wear Jeans and a Shirt. With the whole getup (belt, nice shoes, etc.).

After 50+ trips, I couldn't do it anymore. Not only was I never on-site first day at the client. There was absolutely no reason to wear what I did.

You have to take off the belt/watch for the TSA. Untie the nice shoes and whatever else I had on.

I just said screw it. I wore sweat pants every time I flew. Every. Single. Time. When I was on line for TSA I flew past because I had no accessories. It saved me a few times running late to the Gate. I owe my life to Sweatpants on flights.

I have been on various long flights (EU<>Asia, EU<>US) and would recommend you to wear whatever fits you best. Sweatpants are incredibly comfortable, so go for it.

What I recommend as well:

• Wear good shoes, no flipflops or sandals. In the unlikely event of an emergency this might save your life. Take shoes without laces.
• The same holds true for shirts and pants: wear linen or cotton wool, no synthetic fibers like Nylon that tend to melt on your skin in case of extreme heat. Linen and cotton wool also absorb sweat, so the smell after the flight is probably better.
• if possible take a fresh T-shirt with you on the plane. Around one hour (later the toilets might be crowded) before landing, change your shirt.

To add at least one anecdote about East Asia: I have flown from Paris to Tokyo and back in Sweatpants and had a normal experience. No comments, stares or anything like that.

Neither border agents nor flight attendents will look at you funny. They are used to people wearing whatever is most comfortable, especially on a long haul flight such as yours.

However, don't forget that there's AC running on the plane, so it could get quite chilly, especially if you're sitting for hours on end. I would advise not to wear (sweat)shorts, even though they might seem comfortable.

Back in the old days when gate attendants had a lot of leeway in deciding who to upgrade if necessary (economy overbooked, spaces in business) then wearing smarter clothing was one potential point in your favor. These days upgrades are so rigidly prioritized based on Frequent Flyer status, ticket bought etc that it is almost certainly not relevant.
But if for some reason I was flying in business or first class then I would still dress up better.

There is one important case no one covered in which you need to dress up for a flight.

If you're getting extremely discounted tickets because you or a relative works for an airline, then most airlines have a dress code which will apply to you.

A recent example of this was the two girls who were denied boarding on a United Airlines flight for wearing leggings.

What the outraged Twitter poster (and the mostly information-free media reports) completely missed is that the two girls were travelling on a "companion pass", one of the heavily discounted airline tickets specially designated for employees and family of employees. In exchange for receiving these substantial discounts, these travelers are expected to dress nicer than the average traveler, because they're regarded as representing the airline.

I myself traveled on such a pass from Chicago to Paris about ten years ago (my brother-in-law works for a major airline). I wore a button-down shirt, slacks, a belt, and nice socks and shoes. I wouldn't call it comfortable travel attire, but the round-trip tickets were dirt cheap (I can't recall the price, but around $100 or less). It's especially irksome because the tickets are standby-only; the first day the flight was full, and the second day I got on but was stuck in coach. But hey, cheap tickets.

If you're traveling on this kind of pass, you should discard all the other advice given here and go by the dress code the airline gives you. (If you haven't been told about a dress code, you should ask!)

I travelled from Europe to New Zealand las April, wich were 2 10+ hour flights, so I had lots of doubts about what to do.

So I asked a friend that travels overseas a lot for work and he told me to wear some jeans but pack a sweatpants on my hand luggage, on takeoff wait for the seatbelts signal to switch off and change to the sweatpants and change back to the jeans 1 hour or so before landing.

I did this in all the long flights and they couldn't have been better. If you really care about your appearance or think is going to be an issue going to customs I really recommend doing this. I mainly did it because the sweatpants I had were really worn out with some holes but man, they're really confortable.

On many long-haul flights where sleeping is expected the airlines will provide pajamas to their first-class passengers.

Flying used to be special and something that very few people did and, as a result, people often dressed up for their flights. Today, flying is often seen as a chore and just a convenient way of getting from one place to another. We've gone from planes that seated many fewer people where real meals with silverware were served to massive planes where one is often served out of a cardboard box.

If first-class passengers are walking around in pajamas, I wouldn't worry too much about sweatpants anywhere else on the flight. No matter where you are someone will have an opinion on how you're dressed. I would personally find sweatpants to be too hot for a long flight but it's your comfort that matters.

No.

A lot of people (in my experience) tend to wear sweatpants (UK: jogging bottoms) on flights, especially long haul.

On a flight, you shouldn't aim to be the most fashionable but the most practical.

The main thing is to be comfortable: don't wear something that looks nice but won't be comfy to sit in for multiple hours with restricted movement.

It goes without saying that you can, in general, wear whatever your want. It is also clever to dress up comfy for a long-haul flight. And no, your won't get arrested for wearing sweat pants...

Cultural perception of sweat pants in public varies a lot throughout Europe. They may be fine in London, have a "lower class" connotation in some places and are unthinkable in others. However, that doesn't really matter on long-haul flights: If you wear sweat pants, people will rightly assume that the reason is comfort.

Also, if you need (or want) to look smart before and after the flight, just put some sweat pants (or even pyjamas) in your hand luggage and change on board. You can also bring slippers and take off your shoes (some airlines even provide them).

There are two issues here:

1) Comfort -- the issue which has been addressed by most other answers. I must confess that I often take flights from Europe to China or Australia/NZ -- often with three legs to the flight and spanning two days. It's no great discomfort to travel in a business suit as I often have to go to work immediately on arrival.

2) Border Control -- coming from East Asia there may be a question in the minds of Border Control whether your intentions of coming to study are what you say they are, or whether you might be using them as a pretext to gain entry without any intention of leaving the country thereafter but rather settling long term and possibly living "under the radar." Dressing at the informal end of the spectrum may not be helpful. Nor would flashing a Rolex and wearing obviously very expensive clothing.

Like it or not, people are very often assessed by the clothes they wear and in my view you'd be safer to err on the side of what relatively-conservative professionals in your destination country wear.