Planes are not, in general, supposed to crash.
There are a lot of systems in place to prevent that outcome! It's a really bad outcome!! If something goes wrong, then that's already an Exception, but there are supposed to be lots of systems to deal with it gracefully. Probably. Irris doesn't actually know any of the details here.
(Though she suspects her daughter does. Including, maybe, secret details that might be relevant to the situation that Irris currently finds herself in. Irris isn't exactly resentful about this. She made certain life choices, that resulted in her looking less legibly reliable to Governance than would be required for her to know all of the things her daughter knows, and before today she mostly endorsed those choices. Just. Sometimes very low-probability events nonetheless happen to you, and then maybe you end up wishing you had done different things with your life, even if your life was entirely reasonable.)
...Even dath ilan, it turns out, doesn't have infinite resources, and sometimes Reality imposes its own basic limits and tradeoffs. Which is why cost-benefit decisions have to be made, even in cases where the downside risk involves the True Death of everyone on a crashing airplane.
They are currently in a situation where having a parachute for every passenger available might at least give each passenger maybe 20% odds of surviving the crash. But even when you optimize parachutes for minimal weight, providing them to every passenger on a major trans-oceanic flight adds up, and. Well. Someone much smarter and better-informed than Irris must have, at some point, done a full analysis, and noted how rare this exact situation should be, and assessed the value of parachutes as opposed to other safety precautions, and eventually concluded that, given their not-unlimited resources, it would save more lives in expectation to invest in non-parachute safety precautions, to address more likely contingencies at a lower weight (and thus monetary) cost.
...She wasn't ever supposed to die. Not forever. Not irrevocably. She was supposed to be there for her husband, if and when both of them wake up in the Future. But that...is not super looking like how this situation is going to end. The plane is losing altitude fast, their predicted ground-interception will be over a rocky mountain range where even the most skilled pilot cannot possibly achieve a safe landing, and it's not even cold enough to vaguely hope that her brain will stay viable enough for her daughter for someone from Exception Handling to reach the site and try to frantically cryopreserve all of the casualties.
There's a four-year-old on the plane. People are trying to improvise a parachute for him. Irris is super not qualified to help with that, but - well, she is actually pretty well qualified to sit with a terrified small child, and calmly tell him all of the stories she still has memorized from raising her own children, and not cry at all.