One or two attentive readers will remember that while visiting the Museum of Flight in Seattle , I found a very strange switch in the cockpit of an SR-71 Blackbird . It is labled “Thunderstorm ON/OFF”.

Now, the SR-71 User Manual can be found online. And on page I-184 the switch is explained. It is not an secret weather control system to induce an artifical thunderstorm to hide the spy-plane. It is just a more powerfull reading light for the cockpit, so the pilot can read the maps even in thunderstorm-light conditions…