The invocations have been changed so that they make sense as maneuvers, and where possible, they have an additional small effect or a rename. Darkness being changed to Darkball for example.
Flight is just given to you at sixth level. It really wasn't economical to spend an invocation slot on it in the first place. You can get a better unlimited duration flight for 20,000 gp in the SRD with a 5ft by 5ft [[SRD:Carpet of Flying|Carpet of Flying]]. If you want practically unlimited, a wand of flight is 11,250 gp. Since a warlock did not need to buy a weapon, one of these can replace them.