(b) Yes, this is the better argument. In Australia, the courts have made it clear that when weighing what practical steps could have been taken to avoid potential harm, considerations of convenience, expense, efficiency and difficulty can be taken into account. Practical does not mean just 'theoretically possible'; it means that reasonable options are available, taking account of all the circumstances.
The practicality of what might be done to avoid harm is obviously balanced against the other factors that are taken into account, such as the probability and gravity of the potential harm. For example, it would most probably be considered practical to provide window cleaners with a safety harness to prevent falls, despite possible inconvenience and cost, because of the seriousness of the potential harm from a fall. In some circumstances it may be sufficient to provide a warning of potential hazards.
In the case-study, there may be practical steps which would limit, if not completely eliminate the harm. While it may be impractical to close or move the airport, lesser steps such as restricted flight paths, restricted activities at night, etc might be reasonable.