The PATRIOT missile error (it wasn't a disaster) was more due to the handling of timestamps than just floating point deviation. There were several concurrent failures that allowed the SCUD to hit it's target. IIRC the clock drift was significant and was magnified by being converted to a floating point and, importantly, truncated into a 24 bit register. Moreover, they weren't "slightly off". The clock drift alone put the missile considerably off target.
While I don't claim that floating points didn't have a hand in this error it's likely the correct handling of timestamps would not have introduced the problem in the first place. Unlike the other examples given this one is a better example of knowing your system and problem domain rather than simply forgetting to calculate a delta or being unaware of the limitations of IEEE 754. "Good enough for government work" struck again here.
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