I am going from Canada to Mexico but I don't want to be dependent on in-flight entertainment. Thus I got seagate wireless plus so I can stream to my iPad. I couldn't find any policies I can use this device during flight or not. At very least I am trying to determine if it is worth asking the flight company?
Airlines provide WiFi onboard and invite you to connect to it (for a fee). To connect to WiFi you must have the ability to transmit (internet requires two way communications). If your device is conforms to FCC power limits on the 2.4GHz bands (or whatever your particular jurisdictions regulatory body is) then your device is no different than any other WiFi device on the plane. They are all transmitters using the same maximum power.
If your airplane has WiFi onboard and let's you connect computers to it then there is no technical problem with using your device.
Of course, if a crew member tells you to turn it off, remember you must comply.
The rules are FCC rules, not FAA rules.
The rules about cell phone signals being off during flight have to do with the technical challenges of mobile phone carriers and their cell sites that have to hand off location info about every device in the "cell." At 600 mph this gets challenging.
A correctly working phone is not going to cause a problem for the airplane's communications or avionics systems, but with literally a million passengers in the air at any given time, the cell towers are going to go crazy. They were designed for driving speeds and slower.
Turn everything off at all times below 10,000 feet. Especially takeoff and landing.
And if any member of the flight crew tell you to turn something off, regardless of their misunderstanding about the rules, laws, safety guidelines, etc. - just follow their orders.
The intention behind is to isolate the electronic devices of an airplane from electromagnetic radiation.
Modern airplanes are pretty well protected at the moment and they don't have any issue of isolation.
However, one thing that is key for authorities is flight safety. So it is better to have stronger restrictions that making any mistake.
So, in order to be able to use wifi on the airplane, you need to have, first the airplane modern enough and the airline shall be authorized by the authorities.
Finally, in any case those radiation devices should be turned off (or in airplane mode) when flying in take-off or landing stages (so the wifi of the airplane does).
My recommendation: ask the airline directly and get information about the airplane you are flying in.
The airlines will be primed to say No. But you will hardly be the only one on board with an iPad so it's unlikely anyone will notice. Turn it off if the plane suddenly pitches nose-down at the beginning of your movie.
However, I question the need. I have a 32Gb iPad and there's absolutely no way I can watch a full load of video on my entire vacation, never mind the flight at each end.