Which statement accurately describes groundspeed in flight-time calculations?

For a route distance over the ground, use $time=distance/GS$. Since a knot is one NM per hour, NM divided by kt produces hours. A headwind reduces the ground component of forward speed; a tailwind increases it, so the statement that a tailwind reduces groundspeed is incorrect.\n\n**Key takeaway:** Use GS—not TAS—for route time and ETA.\n\n**Glossary:** **Headwind component**: wind opposing the route; **ETA**: estimated time of arrival.