DALLAS — Look, up in the sky! It’s a bird! It’s a plane! It’s the most valuable comic book in the world. A copy of Action Comics No. 1, the comic book that introduced Superman to the world in 1938, sold for $6 million on April 4 at Heritage Auctions during the first session of the April 4-7 Comics & Comic Art Signature Auction, which earned a whopping $28.2 million in total. Graded Very Fine+ 8.5 by CGC, this issue from the Kansas City Pedigree is one of the world’s finest copies. Only two other unrestored issues featuring Superman’s first flight — or, at least, his first leap over a tall building — have ever graded higher. There are just 78 copies of Action Comics No. 1 in CGC’s population report, with the grading service estimating there are a scant 100 survivors of the comic book that launched superheroes into popular culture — 100 out of the 200,000 copies printed by DC Comics’ predecessor National Allied Publications. Little wonder copies are so coveted by collectors when they appear at auction. For information, www.ha.com or 214-528-3500.