Is this reasonable? I suspect that the courts would rule that it is not. However the actual reason behind the cancellation will be key to decide if a court challenge would be successful. If it was simply a commercial decision then I expect they could win. If it was for safety ..., that might be more difficult.
Thanks EXxB. Perhaps the airlines should be challenged in the Courts with inserting unfair conditions but who has the money to do that? Perhaps Governments should look at the wording on "conditions". Reasons of safety etc would be a reasonable condition but not because enough seats have not been sold.
In other words they've got you by the short and curlies!