* All the companies than need any engineering based work done can take their pick of the best.
* But remember their normal recruitment channels are still open and feeding potential employees through. They may prefer to hire fresh talent rather than a 50 year old.
* And other engineering companies will be affected. If your aircraft company lays off 30% of its employees then it probably does so because it has less orders on its books. Therefore the smaller companies making parts for the aerospace industry have less orders and will be firing rather than hiring.
* Even worse large job losses tend to be correlated with a generalised or sector wide downturn. So car companies and ship companies and bridge companies may also be in a situation where there is less demand and be firing rather than hiring.
* The local economies of the places where the engineers were fired from will be affected. Skilled workers tend to support several service workers and when the skilled workers are laid off the service sectors are affected (you don't go out to a restaurant or get your house done up if you've just lost your job).
* If people move away from towns/cities due to lost work then the property prices tend to fall. A family with a mortgage may be (or feel that they are) better off holding onto their home and accepting much lower pay than accepting they have lost several $100,000 on the re-sale price of their home.
IBM was one of the few American companies that had no layoffs during the depression in the 30's.
Inventories built up. No sales. And he was almost fired.
Once the recovery started every company and govt in the world wanted a computer and the rest is history.
Also, things are a bit different today: IBM is largely a services company, which doesn't lend itself well to inventory building. Also, they have struggled on the merit of their offerings, not the economical climate, for a very long time. Doubling down right now is not obvisouly going to end well.
Disclaimer: this doesn't mean I'm better at the job search. I'm definitely not, and I'd be in the exact same position, of working bad jobs or mooching because I can't land anything between grocery store cashier and engineer. And a big part of the problem is thinking that e.g. someone capable of doing all the math involved in engineering "can't possibly" do the work of an accountant.
If the economy is down then companies don't hire many accountants, actuaries or analysts for the same reasons as they don't hire as many engineers. They also cut down on sales, management and most white collar jobs (and blue collar). So the hypothetical engineer is competing with experienced people for too few of these jobs as well. Similarly many companies prefer to hire recent graduates in these roles for the same reasons as with engineers.
Many middle class jobs also have a qualification based barrier to entry (e.g. from your list accountants and actuaries in the UK+) that makes a career change difficult in good times let alone bad.
+ the training for both of these is usually on the job but why would you hire an ex-engineer you need to train in a job market where excellent skilled hires and fresh young graduates are plentiful.