The airlines have no limit, this limit is imposed by airport security and varies by airport and country. Some are fairly consistent and strictly enforced (e.g. USA) and others have no limit (e.g. Australia domestic flights). Rather annoying is when you have a transit and different rules apply (causing abandonment mid-trip). Lots of other carryon limits too these days, not just liquids, and the new scanner technology is pretty good at picking up these items.