Hi, this is my first post on this forum. I was going to ask the same question as Stuartm but thought I'd tag on this thread.
Firstly I want to say how fantastic Plane Finder is. I live in Biggin Hill, Kent, UK and we get planes flying directly overhead to and from London Heathrow. It's great now that I can know everything I wanted to know about the planes flying over.
Back to my question. I assume when you follow a flight, say from Heathrow to Copenhagen, the red 'tail' shows where the plane has actually been and the blue 'tail' is the estimated location until the screen has updated. When I followed the plane to Copenhagen all was well until it got to 5 minutes before landing. Then the blue line just got longer and longer as the plane flew straight and level, passing the airport. Then it disappeared. I found another plane coming in to the same airport and it did the same. Then I tried it again in on a plane bound for Hanover, Germany. Once again it flew by on the same heading and height then disappeared.
(I might have got the colours of the trails wrong but you get the idea)
It's as though when the planes get close to the airport something blocks the signal and it runs on estimated flight path only. I am only guessing. Is there any reason for these occurrences?
Tony at Biggin Hill.