I"ll be blunt, I'm a big guy (6'5" and 300 pounds) and so I've always avoided flying because I don't want to make anyone else uncomfortable.

I've got to get to Alaska next month and it takes much too long to get there and back any other way. It looks like my options are Delta, or Alaskan Airlines.

I've looked up the width of seats and my shoulders are wider than that. First class is 21", other seats are 17". I'm about 24" across at the shoulders.

Am I better off getting a first class seat, or two economy seats? How does the two seat thing work? Do the armrests come up so they act as one seat? I'd love to experience first class, but I just don't want to ruin someone else's flight.

First is likely your best bet if you can swing it. The First Class seats have a shared armrest between them that is about 8" wide, so you should have plenty of room for your shoulders. A lot of bigger folks go with row 1 as well. The leg room is pretty terrible, but you won't have someone reclining into your lap...

I'm very broad shouldered (wider than you), and can reassure you that if you book FC on Alaska or Delta, you will not encroach on the other passenger. I highly recommend you pick an aisle seat, though, the fuselage curves in and windows don't always align with your shoulders. The aisle also gives you a little more space to lean into if you felt the need, and less bulk to squeeze past someone if getting up.

You can buy two economy seats but you can't buy "Basic" tickets because you will need to have a prior seat assignment to get them together. Each airline has their own process on how to book them and I don't know if you'd have to possibly pay for 'preferred' seating on top of the main cabin prices. The second ticket earns no miles, which is part of why one FC seat is better.

And FYI I know it isn't applicable for a trip to Alaska, but Southwest has a very generous "Customer of Size" policy. You would book two economy seats following their instructions, and when you check-in they update your reservation to give you pre-boarding so you can select two seats together, and a "reserved seat" slip, and best of all they will refund the second seat!!

Where are you flying from?

I am a large guy myself and I am quite comfortable in First. I don't suggest the bulkhead (first) row - they often limit the legroom available and you have no room to put stuff. Absolutely avoid them in coach - they have the trays in the armrests and the seats are even narrower. Also, I would look to see if you can find an A320/321 versus the B737s on this route.

You will get more width space by booking two coach seats, but you won't get as much legroom, nor meals, and the seats are not as comfortable themselves. On the Airbus especially, in first teh seats are a tad further away from the side walls, so you get a little more shoulder room there as well.

I don't know if this will bring you comfort or not, but I'm *almost* your size (6'4" 280 with wide shoulders) and while flying is often less-than-comfortable, you will be just fine and probably won't even be the biggest guy on your flight. I've flown a ton of different airlines and sat in a wide variety of good and bad seats over the years.

Obviously an F seat is the most comfortable. Either window or aisle.
An extra-legroom economy seat on the aisle is your next-best choice because you've got the shoulder room. Just take care to let the flight attendants and drink cart pass by.
A regular-legroom economy seat on the aisle would be a bit uncomfortable but survivable as long as you avoid Spirit and the ilk.
Window seats in coach will likely be uncomfortable because of the shoulder room, regardless of the legroom.
Exit rows and bulkheads sometimes have fixed armrests, making the buttspace feel a bit narrower.

If you are seeing good value in an F seat, great. I know Flyertalkers all have slightly differing opinions on what constitutes "good value" in F. On Alaska, when I see it for my regular midcon 1200-ish mile flight for $100-125 over the coach price, I consider that "good value" and buy it. But if you don't see F seats fit whatever you'd like to spend, I'd book the cheapest Y ticket and pay for an extra-legroom Y seat ("Premium" on Alaska, Comfort Plus on Delta) and you'll be fine. It's unlikely that you would need two seats.

I always take a quick look at seatguru.com if I'm flying a type or airline I've never been on before. It'll show you rows that don't recline, rows with fixed armrests, etc. It'll also show you all of the width and pitch data for each aircraft type.

The seat widths are the space between armrests. You'll have extra width in F because of the armrest as others have mentioned.
That said, if you get an aisle seat, you should be fine in economy. I'd recommend an exit row. FYI, there is generally a little switch under the aisle armrest, which will let you raise the armrest and give you an extra 2in.

I'd say go with FC. It might actually cost more to buy two economy seats. I just flew from YYZ-ANC on Delta and the difference between economy and first class was only $150 each way (it was a B fare though)

Actually, I am going to go against the aisle seat recommendation. The problem with the aisles is you always have people bumping into you. The window seat gives you the ability to lean to the side without worrying about people bumping into you. Now a lot is going to depend upon which planes and how long a flight - a 5-6 hour flight you wont have as much going on in the aisles except at meal times, whereas a short flight most of the time will be spent with carts in the aisle. Also, different planes have different side curvature, and space between the window seat and the wall.

Definitely fly First Class if you can afford it. Not only will you be more comfortable on the plane, the whole flying experience from start to finish tends to be better.

Thanks for the feedback guys. I'm glad to hear that I should be fine in First class. I can afford it, and it's something I've wanted to experience at least once. I was just worried about not having enough room.

Id honestly rather deal with that than getting a weirdly aligned seat. For example, the WN 738 exit row on the left side lines up terribly with the seat. I had a completely full flight an it was fairly uncomfortable.

Firstly let me thank and congratulate you on being so considerate of your fellow passengers, many large people are not. IMHO go with the first class seat, as this is your first flight for a while you might as well enjoy it!