In The Tryals of John Rackham and other Pirates (1721) it is mentioned that Rackham flew a white flag. No flags are attributed to him in A General History of the Pyrates. The iconic skull and crossed swords was first attributed to him in a German book by Hans Leip called the Bordbuch des Satans (Logbook of Satan) first published in 1959, later reproduced in the illustrated book The Pirates of the Spanish Main by Douglas Botting, published in 1973.
Even if it’s not an authentic pirate flag of the Golden Age, it’s still my favourite.