Well explained!

It's good manners to have it off or in airplane mode during take off and landing of course :>
And then generally people are encouraged to turn their phones back on Normal during flight... but it would be best to inhibit anything but the plane's locally offered wi-fi.

"plane's locally offered wi-fi." That is an interesting idea. Once the cell phones reach the plane's Wi-Fi, would they reduce power and not blast the ground towers. But then is the plane's Wi-Fi blasting the ground stations? This will require more reading on my part.

Diving into more reading has unlocked a deeper understanding! As we know a turned on cell phone is constantly searching for a cellular tower connection. In fact, on an airplane, it might emit a stronger signal than it would in a city where towers are closer to the cell phone. This powerful signal could potentially interfere with the plane's instrumentation, but most sources state modern planes have excellent shielding to prevent such issues.

However, when a plane is cruising at high altitudes, cell phones on board can't connect with ground cell towers. This is because the towers are designed to send signals sideways, not upwards, and the typical cell tower coverage radius is only 1 to 3 miles (5,280ft to 15,840ft). Considering that long-haul jets cruise between 30,000 to 42,000 feet, the distance makes connection impossible. But during takeoff and landing (i.e. lower elevations), fast-moving cell phones could connect with cell towers and pose a problem.

But here's the exciting part! Many airplanes now offer Wi-Fi access to passengers, utilizing special ground stations that point upwards along flight routes or satellite connections. Some planes even offer cell service through mini cell towers installed onboard. These mini cell towers convert the cellular signal and send it over the plane's Wi-Fi link. So with a cell tower inside the plane, cell phones would not need to try to connect to any other cell tower; even at lower elevations.


**** A FEW ARTICLES *******************
Where does an aircraft, providing WiFi during flight, get connectivity from?
https://www.quora.com/Where-does-an.....nectivity-from

Frequent internet connection drops or interruptions due to low-flying aircraft
Apr 2024
https://community.t-mobile.com/cove.....aircraft-56875

Can You Use Your Phone on a Plane? Furthermore, Should You?
By: Patrick J. Kiger & Marie Look
Updated: Mar 6, 2024
https://electronics.howstuffworks.c.....-on-flight.htm
"So, how is it that some planes offer cellular service on board? There's a technology that allows passengers to make phone calls without the risk of interfering with the plane's electronics or ground networks.
As Bilén details in his article, picocells — basically, a miniature, low-power cell tower installed on the plane — allow phone calls to be transmitted over the aircraft's internet connection."

Cell Tower Range: How Far Do They Reach?
By Adam Simmons
January 14, 2024
https://dgtlinfra.com/cell-tower-ra.....how-far-reach/

Thanks for the additional data, Mr Bear!

welcomes. Life is always an interesting study.