FDIO message field 05 contains which data element?

• A. Speed
• B. Time
• C. Route
• D. Remarks

Answer: (A)

In this FDIO message structure, each field carries a specific data element, and field 05 is designated for the aircraft’s speed. This is the data the controller needs to gauge how quickly the aircraft is moving, which directly affects timing and spacing calculations. Knowing the speed helps with estimating arrival times at fixes, determining whether to issue speed restrictions, and coordinating with other traffic.

Speed is typically expressed in knots (or sometimes as Mach for high-altitude traffic), and having it in a dedicated field allows the rest of the message and the air traffic system to interpret and act on it consistently. Other data elements, such as time (timestamps or estimated times of arrival), route (the planned path), or remarks (free-text notes), are carried in different fields, not field 05, which is why speed is the correct element for this field.