I'm sure that this chap (who I don't know) will have given the university his due notice: depending on the contract he had, it'll have been either 1 or 3 months, and given the lack of workload control in most university engineering departments, he was probably owed 3+ weeks of leave at any time. The result is an apparently very short notice departure.
In an ideal world, the academic staff would all cross-brief their material and learning objectives - in practice this very rarely happens, and in particular because the academics work such long hours, nobody is going to start sitting in on colleagues lectures to ensure that they know each others material. Also teaching material is (c) the individual academics, not the university.
Additionally, high quality aerospace academics are incredibly hard to recruit - particularly anybody with significant engineering industry experience, because universities (who tend to be very centrally managed and look at the world with blinkered academic eyes) are much more interested in research publication and grant experience, than they are in subject knowledge and teaching ability, which tends to come from industry not another university.
Students will always suffer when academics leave at short notice, and if you have somebody particularly critical to their course material, you've got a particular problem.
Is there a solution? No, there isn't. Is there any point in blaming the individual?- not really, he was probably given little choice by circumstance. The students trying to make sense of the course, and the academics trying to pick up the pieces, just need to make the best of it for the year or more it'll probably take to replace the chap.
I sympathise, the system is poor and does you few favours - but there's little point in blaming the man who was presumably doing the best he could whilst employed but has made a career move, which anybody is entitled to do.
G