Litigation between National Comics (the predecessor to DC Comics) and Fawcett Comics lasted for 12 years. The dispute was concerned with an allegation of copyright infringement by Fawcett of National’s intellectual property rights: that Captain Marvel was too similar to Superman. In 1951, the US Court of Appeal agreed. The cape, the super-strength, the power of flight: in contemporary times these attributes are so commonplace that they are regarded as archetypical elements of the classic superhero.
By 1980 DC Comics had acquired the intellectual property rights to Captain Marvel. Indeed the character was extremely similar to Superman and was not especially commercially successful. Trying to distinguish the two characters from each other in stories was a challenge for writers. In one amusing panel in a 2002 story featuring both characters, the villainous Despero cracks together the skulls of Superman and Captain Marvel. Amidst the violence, the faces, general physiology, and powers were identical, and only the costumes were different.
Now, in 2016, it seems DC Comics have decided to address this. Shazam, as the character has been called since 2011 (thereby avoiding the longstanding issue with Marvel Comics over the use by both publishers of the name “Captain Marvel”), has been disconnected from a mystic link to six Roman gods and Greek heroes of antiquity. Instead, the character draws new abilities from six fictional gods, one of which appears to be Martian. As a result, the character is no longer fast or capable of flight, and instead is immensely stronger than before and projects flame.