Blue segmented line

What is the blue segmented line on the map? I see it between an airport and tracked flight usually. Thanks in advance.

From the Frequently Asked Questions:
Maps

What, exactly, is represented by the flight route line on a FlightAware map? (Back to top)
The solid line displayed on a FlightAware map is a connected series of points between every position report received for that aircraft. Generally, we receive a position every 15-60 seconds.

The dashed line is the planned route of flight per air traffic control. Often times, a flight will deviate from the planned route due to weather, shortcuts, traffic, or other operational factors.

There is more information on it in the FAQs