Learn English – Why does “all to the mustard” mean excellent

The meaning and origin is covered in this article on The Phrase Finder. An extract:

Meaning

Decide a course of action as you go along, using your own initiative and perceptions rather than a pre-determined plan or mechanical aids.

Origin

This is early aviation parlance. Aircraft initially had few navigation aids and flying was accomplished by means of the pilot's judgment.

This Sydney Morning Herald article also says that before advanced instruments, pilots would have use the feel and slide of the seat to tell how the plane was moving.

Yes, warrant is a verb here, in the meaning of justify or necessitate. Further bulletins will be issued if and when required by future events.