Lightsticks

Light sticks are plastic tubes filled with two chemicals separated by a thin membrane. Bend the tube and the membrane breaks, mixing the chemicals which give off a useful amount of light, without any heat, and lasting for up to 8 hours.

Keep one in the bottom of your flight case and with a shelf life of several years, you should never again need to worry about being left in the dark.

Also great for parties, barbecues, bonfire night etc...