Final answer:
The ELT is a mandatory piece of equipment on aircraft, but there are exceptions where it may be permissible to fly without one. These exceptions include operating under a special flight permit or in a closed area with search and rescue services available.
Step-by-step explanation:
The ELT (Emergency Locator Transmitter) is a device that is used to transmit a distress signal in the event of a crash or emergency landing. It is a mandatory piece of equipment on all aircraft. However, there are certain situations where it may be permissible to fly an aircraft without an ELT.
One example is if the aircraft is operating under a special flight permit issued by the aviation authority. This permit may be granted for ferry flights, testing, or other specific purposes where it is not feasible or necessary to have an ELT.
Another example is if the aircraft is operating in a closed area, such as an authorized military or government airspace, where search and rescue services are readily available.