The main purpose of an aircraft's tail is of course to keep the plane in the air. But its secondary purpose is, in the world of business, massively important too.
Just like a brand on a can of drink or clothing, airlines want to be recognised and stand out.
In recent years, with the rise of budget airlines, it's become more common for the name of an airline to be written on the tail. Think JetStar or EasyJet.
The logo or image emblazoned on the tail of an airline's fleet can form the core of a company's branding and identity, and some have had the same iconic design for decades.
So how well do you know the airlines of the world?
Take this test and see how you go.