[santobr]

It's a typical wrong speed in the bombsite.
The crosshairs moves only when the bomber's speed is different from the bombsite's speed.
Try to change the bombsite's speed after lock and you will see the crosshairs stop moving.
There is a table in the online manual with the IAS and TAS in relation with altitude.
You see the IAS in the game and game panel and you calculate the TAS to input in the bombsite.
Again: IAS = Indicated Air Speed; TAS = True Air Speed