Originally Posted by
GlenQuagmire
When I have been issued a block clearance I use the phrase in the block FL430-490 and don’t refer to my current altitude. I don’t really know if that’s exactly right but I copied it from an American pilot I flew with (super bloke even though he later voted for Trump) and it seems to work. I have only ever been given block altitudes in European airspace by military controllers when conducting air tests, never for enroute.
In FAA land, the specified phraseology for issuing a block clearance is: MAINTAIN BLOCK (altitude) THROUGH (altitude) So I use pretty much that "Maintaining Block 10,000 through 14,000" "IN the Block XXX-YYY" is common too. Agree that it's best not to report the specific altitude you're occupying at the time, and It could lead to misunderstanding if the block altitude clearance is forgotten or not passed on to a subsequent controller.