A method for operating a cryogenic rectification column for the separation of the components of air by cryogenic rectification, whereby the column may be operated above its design capacity without encountering flooding, by passing vapor upward through the column at a flowrate which generates a pressure drop within the column of at least 0.7 inches of water per foot of packing height through a height of defined structured packing sheets having a structure in their bottom portion which differs from the structure in their middle portion and is the same as the structure in their top portion.