Jeff Hoy, American

This is a simple run down of how common radio frequencies and bands of the r/c hobby are used and restricted.

• 27 MHz  is open for surface or aircraft use (specifically on 26.995, 27.045, 27.095, 27.145, 27.195, and 27.255 frequencies) but must  not cause any interference of CB radio.
• 49 MHz (specifically 49.830, 49.845, 49.860, 49.875, 49.890) is open to surface or aircraft.  Any transmitting device operating on this band is limited to 100 milliwatts of power.  Because of that it is not recommended to use this band for r/c aircraft.
• 50/53 MHz, also known as 6 meter band, is open to surface or aircraft use by licensed amateur radio operators (HAM radio licenses) only.
• 72 MHz radios, specifically frequency channels 11 through 60 in the 72 Megahertz band, by FCC rules, are restricted to model aircraft use.
• 75 MHz band radios on frequency channels 61 through 90, by FCC rules, are  restricted to surface model use only.
• The 2.4 GHz band is open to surface and aircraft model use.  So if you have an eight channel airplane radio system that you want to use in a custom r/c car or truck you are free to do so.  The 2.4 GHz band is considered by the FCC to be unlicensed spectrum.

27 MHz, 49 MHz, and 2.4 GHz are consumer product bands.  All kinds of consumer equipment, beyond r/c vehicles, make use of them.  Garage door openers, cordless phones, wireless networking equipment (Bluetooth, Wi-Fi, etc.), walkie-talkies, baby monitors, and a lot more use these bands.  In general the only restrictions on usage are devices must accept all interference, must not cause interference on adjacent frequencies, some limits on transmitter power output, and what types of information can be transmitted.

If you aren’t in the USA, this info doesn’t apply to you, check your nation’s laws.

Sources:  AMA, FCC, Futaba, Vantec, Wikipedia