I fly United and the situation is a little confusing. The DirecTV equipped aircraft that fly on that route do not have wifi coverage over the Pacific, whereas their other wifi system does. It works fine over the ocean in my experience. However, the flight crew often still announces that the wifi won't work over the Pacific (I guess out of habit or confusion from being on DirecTV aircraft?) even though this contradicts reality and the material in the united in-flight magazine. The "inflight entertainment" section should tell you what type of wifi you will have, or the safest bet would be to avoid United 737 aircraft on this route if wifi is a priority.