...nor the only airline with 31" seat pitch in back...
First Class on the 747-200 is great. Seats are the standard 64" pitch (or so), which is actually VERY generous. I can almost fully recline in the seat [sleeping is very easy, and I'm not one to sleep on a plane]. On the 744, First is wonderful. The brand new seats recline almost flat, and have the same 64" pitch as the -200's do. PTV's with DVS9 (Distributed Video System-9 Channels) as well as an in-seat video player make the time go much quicker. Lumbar, noise-reduction headsets and great food make it even more perfect. The 747-400's equipped with the new United First Suite are heaven. That's all one can say. Stretching out and sleeping for three hours on a HNL-SFO flight (Dep 1300 Arr 2000 hrs.) was great, and the hot Mrs. Field's cookies and an icy-cold glass of milk before turndown service was a great touch. What happened with the other two hours of the flight? A great meal and movies galore! Sidenote for the UFS: It is a really akward feeling on takeoff and landing. The plane is going forward, but you are angled towards the side...VERY weird feeling!
Business is where I've flown the most on the 747-400 (Mainly First Class for me on the 747-200/-100). The new United Business seats are very comfortable, functional, and stylish. PTV's work well, seat pitch is fine...fairly easy to sleep in. If you are ever in Business, I suggest the window seats in the bulkhead row of Upper Deck-recline the seat all the way, and use the side storage bins as the rest of your "Business bed". With the correct amount of pillows supporting your back, the surface actually becomes flat (almost as good as the United First Suite).
United Economy is average. I flew in 'back' on a SFO-NRT leg just a few weeks ago. I wasn't expecting much in the way of comfort (as it IS Economy), but was pleasantly surprised at how rested I felt once I deplaned in Narita.
Lack of space all around you (especially to your sides)wasn't too fun, however, sleeping was no problem. Don't put anything under the seat infront of you, recline as far as possible, and stretch out. Just as good as a bed! (LOL!).
Meals were quite decent. All three were very filling on the way over.
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