One poster got it right: Inertial frame of reference.

Quoting Seanp11 (Reply 16):
*if you head north, the earth's angular velocity will drop relative to you.* |

Not angular velocity. If any two points (besides the true poles) on the Earth moved at a different angular velocity, they wouldn't make a revolution every 24 hours, and things would be very different.

Before you take off, you're already moving with the Earth. To simplify things, assume you take off to the true North, and land to the true North, and your destination is due North of your departure point, and there are no winds.

When you take off, you're moving with a certain angular velocity; it happens to be one revolution in 24 hours. The destination runway also goes around at one revolution every 24 hours. Mr. Newton tells us that if we're already moving, and we don't do anything to change that movement, we're going to keep on moving. So we land with the same angular velocity we had when we took off; namely, one revolution every 24 hours. This requires the basic assumptions we made earlier, but it is possible to extend more realistic conditions to the problem and see it would remain the same.

The

**tangential** velocity does depend on your latitude. In fact, it's the product of angular velocity and radius from rotational axis. This is why it takes less fuel to launch a spacecraft closer to the equator. It only matters to spacecraft and not airliners though because even low-altitude spacecraft which enter an unpowered stationary orbit depart the inertial frame of reference of the Earth's surface, but airliners never do.