The distance from the North Pole (90°N) to the Equator (0°N) along any meridian is one-quarter of the Earth's circumference: 10,007.5 kilometers (5,403.6 Nautical Miles).
At a standard commercial jet cruising speed of 480 knots (890 km/h), this flight requires 11 hours, 15 minutes, and 30 seconds in real time.
A common point of inquiry in physics and aviation: "As an airplane follows the spherical curve of the Earth over 90° of latitude, what does an attitude indicator (gyro horizon) display?"
Real aircraft instruments use pendulous vanes (mechanical) or gravity-sensing accelerometers (electronic AHRS) that slowly erect the gyro to the local gravity vertical at a rate of 2°–5° per minute. Because the aircraft only pitches down ~0.13° per minute to follow Earth's curvature, the erection mechanism seamlessly keeps the horizon flat and level (0° pitch).
A hypothetical free gyroscope with no gravity erection remains rigidly fixed in inertial space due to conservation of angular momentum. As the aircraft travels along the Earth's 90° curve, the local ground rotates underneath it. By the time the aircraft reaches the Equator, the free gyro indicates a full 90° pitch-down attitude!