perhaps you have asked these same questions yourselfI was wondering how cell phone signals could reach passengers in a commercial aircraft at altitude when I can't even get decent signal from a cell tower a km away that I have line-of-sight with.
A somewhat satisfying article (link below) from March, 2021 has this in it about using cell phones on planes.
""In practice, at normal cruising altitude of 36,000 feet (11 kilometers) "if you do have your cell connection on in the air, you probably won't get any cell towers," Biln says. "The cell towers don't expect there to be traffic in the air, so their radiation patterns are focused on the ground." It's probably only when planes descend to less than 10,000 feet (3 kilometers), as they get closer to landing, that passengers could flip on their phones, connect and cause interference.
So, how is it that some planes offer cellphone service on board? There's a technology that allows passengers to make calls without the risk of interfering with the plane's electronics or ground networks. As Biln details in his article, picocells — basically, a miniature, low-power cell tower installed on the plane — allow calls to be transmitted over the aircraft's internet connection. Since the early 2010s, Virgin Atlantic, a British airline, has provided in-flight mobile service using that technology. But the service is discontinued once an aircraft is within 250 miles (402 kilometers) of the U.S. border.
Even though it's technologically feasible, don't expect to be able to make cellphone calls on a U.S. airline flight anytime soon. The FCC spent seven years considering a rule change that would have allowed cellphone service on flights, but ultimately abandoned the idea, after it faced intense opposition from a wide range of groups, ranging from flight attendants and machinists and aerospace workers to federal law enforcement officers. As this 2014 comment details, one concern was that phones might be used by terrorists to detonate explosive devices. Another criticism was that if passengers had phones pressed to their ears, they might not hear important safety instructions from flight attendants.
Others objected because they saw passengers talking on phones as an annoyance inside the cramped confines of an airliner. "The last thing any of us need during a flight is to be treated to the loud conversations of others while we're trying to read/sleep/converse quietly with a companion," one commenter wrote." https://electronics.howstuffworks.com/tech-myths/cellphone-call-on-flight.htm -- -- -- -- --
A CNN article from 2014 speaks to the issues, although I expect a few of the answers they offer may be somewhat dated. (It just happens to be an article about MH370.)
https://www.cnn.com/2014/04/14/tech/mobile/phones-in-flight/index.html
"Cell phones communicate through cell towers, which are located on the ground but can stretch hundreds of feet into the air. As an airplane rises, it gets further from these towers and eventually moves out of contact range. For efficiency, many towers are designed to direct their signal where its most useful: on the ground, not into the sky above.
The maximum distance at which a phone can still make calls and send texts varies depending on the type of tower and transmitter, but an airplane would have to be no more than 10,000 feet in the air for any cell phones on board to still have a signal, according to Bill Rojas, director of telecom research at IDC Asia Pacific.
It’s not just altitude that can limit cell phone service.
When flying over sparsely populated rural areas, nearby towers are fewer and farther between. Over the open ocean, there are no towers at all with which to communicate, making phone calls, texts and social media posts impossible.
Speed can also make maintaining a cellular connection difficult, as a device has to switch from tower to tower to maintain a connection. Rojas told CNN that a plane would have to be going 155 miles per hour (250 kilometers per hour) or less for phones in cell-tower range to make or receive calls.
The metal body of an airplane can also impede cellular service."
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"There are two operating systems for airplane Wi-Fi: ground-based and satellite. Air-to-ground Wi-Fi works in a way similar to your cell phone. An airplane has an antenna located underneath its body, which links up with cell towers. As the aircraft travels, it simply connects to the nearest transmitter on a rolling basis.
The airplane becomes a hot spot, so passengers can do everything they would normally do when connected to the Internet, including sending emails, making calls, and even streaming movies. But this system can’t work when the plane is flying over large expanses of water, like on transatlantic routes. That’s where satellite comes in.
Satellite Wi-Fi uses a network of orbiting satellites to allow a connection. The satellite is linked to ground stations, and the airplane connects using a satellite antenna on the top of the aircraft. The plane uses whichever satellite is nearest as it travels. Satellite Wi-Fi operates on two different bandwidths: narrowband and broadband. Both allow passengers full Internet access, although narrowband is less suitable for streaming movies."