Hi Guys, thank you so much for your answers. I'm playing in career mode. The trajectory line was visible up to one point - but i can't identify any special event that triggered the disappearance. vexx32: Happened to me before, but i scrolled around the whole planet - there was no trajectory line at all. Due to another unknown event/accident, my current savegame was deleted (the savegame-handling is a pain in the ***, isnt it?) and I loaded a slightly older one. BAM - trajectory line. I'm now missing a few tricky missions, but thats a price to pay for a visible t-line. Still doesn't know what triggered the disappearance :-( But thank you guys for your answers, it's really nice to meet a helpful community. Love KSP.