As I have worked in the world of EMC compliance for the last ten years (albeit in consumer audio) I thought I could try help clear a couple of things up. Sorry if I get a bit technical....
CRTs don't emit that much RF radiation, there's not really any fast circuitry in them. Anyway, as mentioned before if they are designed to be fitted inside an aircraft they will be suitably screened and tested. Acually X rays are more of a problem with CRTs.
FCC Class B is an RF radiated emissions class. Essentially you go to an open area test site, wave a calibrated antenna at the product at a calibrated distance and measure the RF emissions. If they fall below a certain limit the product passes. Class B means a product can be used in a residential environment. Class A is industrial (an aircraft environment is not mentioned and the FCC did not take avionics into account when they set the limits). An FCC Class B label can mean a) a genuine product has been tested by an approved test lab and the product has passed the test or b) a specially made "get through the FCC test" product has been made and tested or c) the product has not been tested as it would never pass and the manufacturer is lying. I am afraid there are thousands of b) and c) type products in the market.
Power consumption level and whether AC or DC has little to do with RF emissions, it is the type of circuit contained within a device that counts. An analogue tape recorder has only a low frequency bias oscillator. A CD or Minidisc player has all sorts of high frequency oscillators, to work the micro processor and digital to analogue convertor etc, inside it. These oscillators use square shaped waveforms which are bad as far as EMC is concerned as they produce harmonics of the fundamental frequency which can radiate up to the GHz region. Also, these devices are very compact which limits the amount of EMC supression components that can be fitted.
The only way to make a device truly immune to all EMC interference is to completely seal it in a metal box. However you need to get power, interface cables, an antenna etc to it, it may need ventilation. You can filter these ports but not 100%. You can test devices for immunity but not for every conceivable circumstance.
Call me old fashioned but if I were the captain of an aircraft I would not allow passenger electronic equipment to be switched on at any stage of a trip.
Don