Keep in mind there are several types of airspeed.
Indicated Airspeed (IAS) is Airspeed based upon the ratio of stagnation vs static ambient air pressure where the airplane is flying.
Calibrated Airspeed (CAS) is Indicated Airspeed corrected for installation and equipment error. It reflects a more precise airspeed at STP based upon the installation.
True Airspeed (TAS) is the indicated Airspeed corrected for nonstandard pressure and temperature. It reflects the actual speed of the relative airflow over the aircraft. In still air, the TAS is equal to the groundspeed.
Groundspeed is the speed the aircraft is crossing over the ground at. It will be equal to the sum of the true airspeed of the aircraft and the headwind component of the wind aloft at the altitude the airplane is flying at.
It becomes important to differentiate and understand these terms as they will play an integral role in your time distance and fuel calculations in order to know whether you can safely complete a flight. Flight planning does not use linear range as a metric so much as it relies on total available time aloft. Fuel tanks carry known quantities of fuel and engines burn fuel at specific rates at specific power settings at specific altitudes resulting in specific true air speeds during the climb, cruise and descent portions of the flight. Divide the total fuel on board by the rate of fuel consumption, and you know your total flight time available. You will then need to know the winds aloft information to calculate your forecasted groundspeed in order to know if you can safely complete the flight.
Fail to perform these calculations correctly, and you could face a forced landing or a ditching from fuel starvation. If upper level winds are stronger than forecast on a fuel critical flight i.e. one that's planned to be very close on fuel aboard, you will need to be able to make these calculations en route to know whether you will need to divert to an alternate airport or you can press on to the planned destination. This happens a lot both with small aircraft as with this SR-22 which ran out of fuel due to strong headwinds while on a ferry flight to Hawaii and even in large jets. Bangor International in Maine is a alternate for aircraft crossing the Atlantic who get into trouble as is Hawaii and Samoa for Pacific Rim routes.