Pilots behave in what manner ?
They are rostered - they fly their allocated roster. It's not an industrial tactic, it's what they're told to do by their employer. And they do it, quite competently.
The Engineers behaving in what manner ?
Too much work allocated for the full time staff complement to carry out without compulsory overtime ? I understand it's efficient for a company to run at 20% overtime but by all definitions in EVERY SINGLE workplace agreement, overtime is voluntary.
Being that it is actually, voluntary, it can be withdrawn at will, officially and unofficially. Hence there is 2 sides of the coin here. The employees may want the cash or they may not want the cash. The company may want the staff to do overtime or they may not. If it gets to an inflection point where the staff choose to not do the overtime when the company requires it, then we have a problem.
Hence the reason why it may be good business practice to run at a deficient workforce number to manage peaks and troughs in demand, it runs counter intuitive to run said policy, when you have a policy of total disengagement running at the same time, consciously or not.