I work for an airline (cabin crew management). We face a lot of passengers who have issues with masks, but we aggressively enforce it. We simply remove those who decline to wear the masks from the flight. If a passenger removes it during the flight and declines to put it on again, airport security will be waiting for him/her after landing.
What can be done if the airline does not enforce this while the law requires it?
Reputation! go online (it seems you’ve already done this) and post some photos (if this is allowed where you live), report them to the civil aviation authorities, airport authorities or health authorities (they love to collect fines, airlines hate to pay them), leave comments at the airline rating websites (such as airlinequality.com).
Low cost carriers do not have much to offer beside the low prices and the promise of taking you safely from A to B, they cannot afford to lose that. And remember, although the authorities take time to respond, but they usually do. Most likely they will not respond back to you, but for sure they will contact the airline.
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