I'm no legal eagle but I question the legality of changing these rules overnight without a fair and adequate period of notice. As a Miles & More FF, I recently purchased a cabin bag from the Lufthansa shop which boasted it met their (and most airlines') maximum cabin baggage dimensions. Although it fits snugly in even the smallest commuter aircraft, my bag now technically fails to meet one of those new "IATA" dimensions by 6cm. I therefore wonder if they could face litigation by a determined and organised group of their own disgruntled frequent flyers?