Dimmable fluorescent lamps were used in at least one airplane built by the now deceased Beech Aircraft Co ca 1970, using "conventional" fluorescent tubes but with radio-frequency power in place of the usual 50/60/400 Hz generally available on aircraft.

Numerous inquisitive kids back as far as the mid to late 30s learned about the "dimmability" of fluorescent tubes when they built their Tesla Coil generator - from a kit or from scratch. It was probably harder to find a fluorescent tube in the earliest of those times than it was to build the means to excite one.

It remains quite simple to light up a fluorescent tube at variable intensity; but lighting the lamp without spurious rf noise that interferes with all the other electronic junk that surrounds us remains much more difficult; and not all the devices offered for sale now actually achieve "emission free operation" - hence (in part) the difficulty of making a particular one available in all markets due to varying concern about "EM noise" on the part of regulators.

John