We've all learned a lot about what can and can't be done from the tragic story of MH 370, as well as the Air France flight lost over the Atlantic. Of course, nobody expected the real transponders to be disconnected or fail, and so it may be silly to speculate about how to avoid this situation when there already is supposed to be a system that stops aircraft from getting lost. Even so, here are some things to consider:

In the next few years, Iridium plans to launch a new generation of satellites with 1 megabit of bandwidth, replacing the pitiful 2400 bps they have now. In addition, with luck, Google Loon may get launched and do even more. With that much bandwidth, you can augment the "black box" with a live stream of the most important data. In particular, you would want a box to transmit as much as it could in the event of catastrophic shock, loss of signal from the aircraft and any unplanned descent, including of course getting close to the ground away from the target airport set at takeoff. Even the high cost of Iridium is no barrier for rare use, and you actually have a lot of seconds in the case of planes lost while flying at high altitude. Not enough to send much cockpit voice, but the ability to send all major alerts, odd-readings and cockpit inputs.

You could send more to geosync satellites but I will assume in a crisis it's hard to keep aimed.

Another place you could stream live data would be to other aircraft. Turns out that up high as they are, aircraft are often able to transmit to other aircraft line of sight. Yes, the deep south Indian ocean may not be one of those places, but in general the range would be 500 miles, and longer if you used any wavelength that could travel beyond the horizon. Out there over the ocean, there's nobody to interfere with, and closer to land, you can talk to the land. Near land, the live stream would go to terrestrial receivers, even cell towers. Live data gives you information even if the black box is destroyed or lost. If you are sure that can never happen, the black box is enough.

It also could make sense to have the black box be on the outside of the aircraft, meant to break away on impact with ground or water, and of course, it should float. The Emergency Locator Transmitter should be set up this way as well. You want another box pinging that sinks with the plane, though. The floating ELT/black box could even eject itself from the plane on its own if it detected an imminent crash in any remote area, including the ocean. With a GPS, it will know its altitude and location. It could even have a parachute on it.

Speaking of pinging, one issue right now is the boxes only have power for 2 weeks. Obviously there is a limit on power, and you want a strong signal, but it is possible to slow down your ping rate as your battery gets low, to the point that you are perhaps only pinging a few times a day. The trick is you would ping at very specific and predictable times, so people would know precisely when to listen -- even years later if they get a new idea about where to look. Computers can go to sleep on these sorts of batteries and last for years if they only have to use power once a day.

If all you want to know is where an aircraft is, we've seen from this that it doesn't take too much. A slightly more frequent accurately timed ping of any kind picked up by 2 satellites (LEO or geosync) is enough to get a pretty good idea where a plane is. The cheapest and simplest solution might be a radio that can't be disabled that does this basic ping either all the time, or any time it doesn't get the signal that others systems like ACARS are not doing their job.

Like many, I was surprised that the cell phones on board the aircraft that were left on -- and every flight has many phones left on -- didn't help at all. Aircraft fly too high for most cell phones to actually associate with cell towers on the ground, so you would not see any connections made, but it seems likely that as the plane returned over inhabited areas on its way south, some of those phones probably transmitted something to those ground stations, something the ground stations ignored because they could not complete the handshake. If those stations kept lower level logs, there might be information there, but they probably don't keep them. Because metal plane skins block signals, they might have been very weak. If the passengers were conscious, they probably would have been trying to hold their phones near the window, even though they could not connect at their altitude.

Another thing I have not understood is why we have only seen the results of one ping detected by the Inmarsat over the Indian. From that ping, they were able to calculate the distance of the aircraft to the satellite, and thus draw that giant arc we've all seen on the maps. It's not clear to me why there was only one ping. Another ping would have drawn another arc, and so on, but that would have given us much more data to narrow down the course of the aircraft, as it's a fair presumption it was flying straight. The reason they know know the one ping came from the southern hemisphere is the satellite itself is not perfectly centered and so moves up and down, giving a different doppler for north vs. south.

We may not learn their fate. I must admit, I'm probably an unusual passenger. I am an astronomer, and so will notice if a plane has made such a big course correction, though I have to admit in the southern hemisphere I would get confused. But then I would pull out my phone and ask its GPS where we are. I do this all the time, and I often notice when the aircraft I am in does something odd like divert or circle. But I guess there are not so many people of this stripe on a typical plane. (Though I have flown in and out of KL on Malaysian Airlines myself, but long ago.)

While hope for the people aboard is gone, I do hope we learn the cause of the tragedy, to see if anything we can think that is not too expensive would prevent it from happening again. The cost need not be that low. The cost of this search and the Air France search both added up to a lot.

Update: A New Idea -- as soon as the search zone is identified, a search aircraft should drop small floating devices with small radio transmitters good to find them again at modest range. Drop them as densely as you can, which might mean every 10 miles or every 100 miles but try to get coverage on the area.

Then, if you find debris from the plane, do a radio hunt for the nearest such beacon. When you find it, or others, you can note their serial number, know where they were dropped, and thus get an idea of where the debris might have come from. Make them fancier, broadcasting their GPS location or remembering it for a dump when re-collected, and you could build a model of motion on the surface of the sea, and thus have a clue of how to track debris back to the crash site. In this case, it would have been a long time before the search zone was located, but in other cases it will be known sooner.