On my 56K connection, the only time I experience "jumping aircraft" is when all our aircraft are very close to the ground and there are lots of
scenery objects that the computer has to cope with displaying, as well as the aircraft.
As an example; flying nose down, closely following another aircraft to land, at an airfield containing many complex objects.
When we are flying in close formation in a clear sky, there is no such problem...

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A mixture of close multiplayer aircraft, and close complex scenery creates the problem, otherwise I have no difficulties in smooth flight on 56k dial-up*.....

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Paul....G-BPLF....

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* for
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.