These complaints are legitimate because as a customer you buy an entire seat. Not half, not three quarters. The way airlines handle these complaints varies. As with many complaints, they are usually ignored, but you need to be persistent in that case, especially if you left the flight because of it. In such a case, you would file an official complaint with your national regulatory body, such as the US Department of Transportation. Cathay Pacific Plus Size Passengers airlines are required to respond to these complaints in light of applicable laws and regulations.