What about this scenario.
BAW 123 clear to join overhead SAM climbing to maintain FL160.
Seems fine
I want to build a bit in so I say BAW123 cross SAM level FL100. I've changed a bit of the clearance but does that cancel the original clearance to FL160 ? Maybe .........
Then I feel bold and say BAW123 cross SAM FL130 or above. Have I cancelled the original clearance or just added a bit ?
Or in another case BAW123 route direct XXX. I have cancelled the original clearance, full route to destination ? No I have just changed an intermediate bit and the rest of the route after XXX remains as previously cleared.
My view is that take off to touchdown ATC is a series of interacting instructions not simple clearances. You comply with them all unless told to ignore or if you think they are incompatible i.e keep your speed up .... then expedite descent !!!
We know that one is popular.
Someone could write a book of rules round this lot and still not capture all the possible scenarios.
