So that I can go online? Does it have signal in the air?
3G or HDSPA modems work pretty much the same way as cellular or mobile phones, so the following article will apply:
Anyone who has flown on an airplane in the past few years has heard the stern warning from the flight attendant about turning off cell phones and other portable electronic devices. Airlines warn that the signals from cell phone transmissions can disrupt navigation systems and pose a danger to the aircraft. But is it even possible to make cell phone calls while in flight?
The simple answer
Following the terrorist attacks of Sept. 11, 2001, news reports carried stories of passengers phoning loved ones in the minutes before the planes crashed. Also, the Federal Aviation Administration has conducted studies indicating that despite the warnings from flight attendants, an average of one to four cell phone calls are made from commercial flights in the United States. Obviously, then, cell phones can operate in flight, at least under certain conditions.
How cell phones work
Cell phones are basically radios which connect to a transceiver located on a cell tower. Each tower covers a certain area, or cell, hence the term cell phone. When a phone moves from one cell to another while in use, as in the case when the caller is in a car, the tower "hands off" the call to the next tower. Cell phones can typically connect to a tower up to 10 miles away.
Towers, however, are configured to connect to signals at ground level, so while someone on the ground or in a car may be able to connect to a tower several miles away, that range is much shorter when flying at 35,000 feet. Also, a cell phone transmitting from a high altitude may connect to several towers at once, resulting in a scrambled signal. And while the cellular network can easily hand off the call of someone traveling at 70 miles per hour, the task is much more difficult when the caller is traveling at 600 miles per hour.
The bottom line
While it might be possible to make a cell phone call while in flight, the bottom line is that chances are the call quality won't be very good, if you are able to connect at all. That may be changing, though. Cell phone companies are in the process of developing equipment that can handle calls from the air.
Unfortunately, allowing cell phone use on airplanes will place airlines in the position of finding ways to control conflicts between passengers because of inconsiderate cell phone use. Congress is considering making the ban on cell phone use permanent, although the wireless industry is resisting such a move. The airline industry will most likely have to develop a solution such as a "no-phone section" in order to handle the changes.
It's bad citizenship to use cellular on a (standard) plane. Because of your altitude, your phone tends to connect to multiple cells simultaneously and use very large amounts of bandwidth. It may be technically possible but it's a violation of the rules of most airlines and it's not nice. Is it really so bad to be off the grid for a few hours?