Mental Math for Pilots Practice Test 2026 - Free Pilot Math Practice Questions and Study Guide

Density altitude tells us how thin the air is; as it increases, the air offers less mass for the wings to push against, so true airspeed rises for a given indicated airspeed. The rule of thumb here is a 2% increase in TAS for every 1,000 ft of density altitude.

Ten thousand feet is ten increments of 1,000 ft, so TAS increases by about 20%. With a sea-level TAS of 120 knots, multiply by 1.20:

120 × 1.20 = 144 knots.

So the true airspeed at 10,000 ft density altitude is about 144 knots.