To be annoyed that DH didn't plan for DS's first day of school?

[AttackCherubim]

DS starts school tomorrow.
DH works in IT for a large company with multiple offices across the country.
They put a new program in place over the weekend but discovered Monday it wasn't working properly.
DH is now claiming he might need to miss DS's first day to work to fix it.
I am annoyed, and he accused me of "minimising his job"

I pointed out that he has had months to book annual leave, there are more than just him and his team, and if my friends husband can make it back from army deployment for their child's first day, he can take the morning off work.
AIBU to be annoyed?

YABU, you don't need two parents to take a child to school.

This! You'll be even more heavily pregnant before baby comes.

Personally I don't think it's necessary. But you obviously do. So in hindsight you should have told him to book a days leave.

I totally understand your annoyance.

It doesn't matter whether others saw two parents as necessary for their child's first day, your situation (special needs and pregnancy) lead to an educated guess it might be really useful.

I would be more than annoyed, as you both are working, you talked (and presumably agreed) you both should be there, and he didn't plan for it, while you did. If you behaved the same way as he, there would be noone.
He makes you a default parent.