On which frequencies do Aircraft Emergency Locator Transmitters (ELT) operate?

Aircraft Emergency Locator Transmitters (ELTs) operate primarily on 121.5 MHz, 243 MHz, and 406 MHz. The significance of these frequencies lies in their designated use in search and rescue operations.

The 121.5 MHz frequency is a distress frequency that was historically used by aircraft in distress situations and can be monitored by search and rescue aircraft, ensuring a broad range of coverage. The 243 MHz frequency is reserved for military use, serving as an emergency frequency for distress. Lastly, 406 MHz is a digital transmission frequency which provides more accurate location information when combined with satellite detection systems.

The choice that includes these three specific frequencies accurately reflects the operational protocols and technology used globally in aviation for emergency situations. The other options either include incorrect frequencies or slightly altered values that do not conform with established aviation safety standards.