Simply put - according to the current EU directive, a specially trained crew member makes a line behind the plane - the so-called "linkerman". It is made so that they can monitor and possibly correct the flight path at ground monitoring stations. This only applies to jets. Aircraft with propellers - in the "helicopters" jargon, the regulation does not apply. .butly, because linkerman did his job - there are big penalties for that. So somehow (dance)