I have a couple of old Futaba Conquest AM radio systems that I purchased in 1986. I am wondering if these radios can still be used for rc aircraft, and how to tell?
Technically there's no reason why you couldn't use them - AM channels are still used occasionally in the 72MHz or 27MHz bands, the latter being used mainly by toy planes etc.
But, personally I'd advise against it if your model is half-decent. AM is more susceptible to interference, and the technology is rather outdated.
A good quality FM radio set - or even 2.4GHz - doesn't cost much these days, and will give you better peace of mind, in my opinion!