Originally Posted by
Gonzo
Departures from LHR must follow the departure route until passing 4000ft.
When it’s busy, they usually continue more or less on similar paths due to the many interactions with different routes to and from all the other airports around London.
With traffic numbers being so low, aircraft are able fly more direct routes, but they still have to comply with the 4000ft restriction.
Though there have been a fair number of easterly departures recently that didn't follow the SID/NPR below 4000'.
Why would that have been ?