Originally Posted by
TonyWilliams
Where it would bite the Local control hard is when a Cessna taxied up to the hold short line (from run-up) without calling ground, and they were IFR (and of course said nothing to Local like, "Cessna 123, holding short runway 26, IFR to Podunk".
The ground control only passed an IFR flight plan to Local when they called from the runup (unless it was a jet).
More than one got off the ground without an IFR release (transparent to the pilot; a serious operational error for the controllers involved).
Releases and the optimum departure sequence are the reasons you
should call ready from the block. without moving up. It allows the local control to put you in the best place in line, or even keep you out of the line if necessary.