[RNCTX]

All cell phone towers seem to be aimed toward the ground.

I've flown a GA aircraft all around the lower 48, and only get a cell phone signal briefly when flying directly over a cell tower.

[Fatnino]

Naturally. Why would a cell carrier want to expend energy beaming signal into space?

That said, you do get the occasional misaligned antenna or weird bounce off terrain that gets you signal midflight for a minute.

[barcoder]

How easy is it to report those type of issues?

[krisoft]

What do you like to report? That cell signal was available somewhere?

[dylan604]

make a phone call, and let the big data folks raise eyebrows when they see the elevation the call was made.

[jcalvinowens]

It's really regional. I get 5 bars pretty much anywhere below 5000ft in the bay area.

[_moof]

Yep, I get signal up to about 3000' AGL where I am.

[supernova87a]

Well, given that the possible range to a cell tower is about 35 km / 20 mi (max, an absolute limitation of how the GSM/timing is done), it's very plausible that even if cell broadcast antennas are generally pointed down + flat with the horizon, you're gonna get some signal from some antenna in the distance.