Therefore I read that as no requirement to file a DLA or CHG message with IFPS (and thus CFMU) if you are +/-15 minutes from EOBT. Outwith the 15 minutes, or if you have a slot, then you do have to make the changes known as per the CFMU Handbook. However, it does not directly mention whether the CTOT has a similar tolerance.
Can we just be clear on this? If the reason for your being 15 mins or more later than EOBT is a CFMU imposed slot, you
don't need to send a DLA message. If that slot is subsequently cancelled, leaving you unable to get off blocks within 15 mins of the original EOBT, then you
do need to send a DLA.