Advice for first time flight alone?

I'm 18 and although a frequent flyer I'm about to fly alone for the first time ever and to make it worse the flight is 15 hours the longest I've ever done before is 11 with family what can I do since I won't know anyone? And any advice for getting through the airport without panicking

There's nothing to panic about.

I would like to know your final destination and your stop overs. More over while booking you can say the instruct the flight company to direct transfer if you travelling by same flight till your destination.

Why do you need to know anyone? Do you expect to know people if you t ravel by train or long-distance bus? This is just the same.
And if you get to the airport with plenty of time to spare (three hours before scheduled departure time is recommended for international flights), there will be NOTHING to panic about.
ASK if you're not sure what to do or where to go: airports are full of first-time flyers and nobody will be surprised if you ask.

Airports have plenty of people to help you, so getting lost isn't going to be a big deal. If the airline has an app, install it on your phone. That can help you keep track of gate changes. Get to the airport with plenty of time, and don't panic.

Just put some candy in your mouth and earbud in ears.
MCA- Irtaza Marketing Associates

There's only so much you can do. Bring plenty of things to keep yourself busy - word and number puzzles, magazines, books, electronics, etc. There will almost certainly be some in-flight entertainment. Take some snacks you like to eat. Plan to sleep for part of that flight. But there's nothing to be nervous about for the flight itself - just keep yourself busy and the time should pass as it would if you had company. And maybe you'll be near another solo traveler and can get to know them.

Sure. Get there with plenty of time to spare ahead of flight time--3 hours is good--read the signs to find out where you should go after checking in, and if that doesn't work then ask someone. Airports have more signage than anywhere else on earth, as well as maps, information booths and boards, staff at various airlines, and other travellers. So what if you don't know anyone? Is there some reason you can only ever talk to people you already know?

Make sure you know where your gate is, be there 40 minutes before boarding time, check the information boards an hour ahead to be sure the gate hasn't changed, don't lose your ID and don't leave your luggage unattended.

I travel alone all the time. It's not a problem. Don't you usually listen to music or watch the movies on the inflight entertainment anyway? So just do the same thing. Get up and walk around every now and then- 15 hours is a long time to sit.

As you have been through Airports many times before what is the real issue. The procedures are the same for a five hour flight an eight hour flight or one of fifeteen hours.
Your total travel time day is from the time you wake up to when you get to place you sleep at destination. Flight is part of it. MOST sleep for a large part of it. Looking at Ocean gets alittle boring after an hour or two.
Of course the concept of reading a book, doing your knitting, listening to some music or playing a game could be done to pass the time.
On a flight this long suggest you make a point of using the ground toilets just before departure. They are much more comfortable than the ones on the plane.
The clock moves by time zone. YOUR BODY does not magically change as the time zones change. You can prepare for this a few days before travel adjusting your eating and sleeping towards the destination schedule. An hour or two each day. You need to do it either before the flight or after. Your total travel day will be closer to about 24 hours.
MOST SLEEP at some point during a 24 hour day. Nothing wrong with having a nap or two during the flight.Helps to be alert when trying to do your passport and customs check at the end of flight.
I assume you have arranged your transportation from Destination Airport to the place you will sleep first night there. Wide awake passengers are not as easily scammed by those trying to take advantage of tourists on arrival.