The worst response to a missed deadline is to manage the news rather than the situation. Leaders who try to soften the communication before they have diagnosed the cause end up having two conversations: the miss, and then the explanation for why the first explanation was wrong.
The first 48 hours need one thing: a clear account of what happened, what it means for the rest of the program, and what you are doing about it. Not a root cause analysis, that comes later. A factual description of the gap and the immediate response. Be specific about what you know and honest about what you do not.
At Intuit, a compliance reporting milestone slipped because a dependency from a partner team came in incomplete. The initial communication to leadership said the team was assessing options. That was accurate and useless. What leadership needed was: here is what came in, here is what is missing, here is who is fixing it and by when, and here is the downstream impact. I rewrote it and sent that instead. The conversation shifted from frustration about the miss to focus on the recovery.
After the immediate response, run a short root cause review. Not to assign blame, but to find the structural issue. Deadlines that slip because of last-minute surprises usually had early warning signals nobody was tracking. The root cause review finds those signals so the next program tracks them.
A missed deadline handled well is recoverable. The same deadline handled badly, with delayed communication or defensive framing, damages something harder to recover: credibility.