Then get to work designing and certifying it.

In the meantime, the next generation of aircraft tracking and distress alerting is GADSS, and more than a few smart people have been working on it. It'll start to be implemented in some countries in 2025.

Feel free to go to the source material at ICAO, read the EASA rulemaking and means of compliance guidance and tell the industry that you're "sure" they could do better.

>You assume that as a plane is crashing, the datastream fails. Why?

1. Connection issues are common problems for normal operations and should be expected for any such system.

2. To communicate the volume of data an FDR captures with satellites you need a high-gain antenna with significant power requirements. To reduce said power requirements a directional antenna is best, such as for Starlink. These will naturally loose connection if a plane is no longer pointed up, such as diving towards the ground and especially diving while inverted. This isn’t GPS where the data transmitted is minimal, there is a massive amount of data in an FDR.

> Given such, any data are better than none.

And the cases of no data are practically unheard of. If you can get to the wreck, you can get to the flight data recorders.

>Last point regarding rarity of use: How often do flight data recorders get read?

Every single time they are recovered, with dozens per year as legal requirements push them to smaller aircraft with lower safer standards compared to airlines. You may not read an FDR in case of a bird strike where the aircraft lands safely, but even then removing them is common.

Name another crash in the last decade besides MH 370 where the black boxes were not recovered.

>The title of this thread marvelled at the technology of the hardware devices. I'm sure a fraction of that technology could make online flight recorders happen.

It is far easier to make anything wired function reliably at high bit rates compared to something wireless. Landlines came a century before wireless phones (satellite or cellular). Wired Internet long predates wireless, and most of the global internet passes along undersea cables rather than satellites. A couple months ago T Mobile and SpaceX announced they were going to used Starlink satellites to end dead zones: these require large version 2 satellites too large to fit on a Falcon 9 and will initially only offer text message support rather than real-time voice calls.

You’re asking for something far more ambitious: real-time communication with thousands of airliners in the air every second with high data output from each. Thus would require massive allocation of radio frequencies (which are already limited) and require thousands of new satellites to function (with cheap launches at about $1 million per satellite using Starlink as an approximation, which is far cheaper than most). All to solve a problem that is so rare it has only been an issue for a handful of crashes over the past several decades (we haven’t even discussed how most crashes are within a few miles of an airport).

This could be solved far more easily by a far simpler solution: every five minutes in the air the aircraft transmits its current GPS coordinates. If it goes down, the search area is now small enough that you can easily find the black boxes.

Your naïvety on such problems shows how little you actually know about the subject and engineering in general. A complicated solution for a niche problem almost never sees the light of day.