User blog comment:SlyCooperFan1/Ace Combat Infinity Update 14/@comment-27807723-20160331070113/@comment-26183061-20160410024808

It means they've left the option open so the *CAN* add more levels in the future; there's still no definite word on when or if they'll do so. The fact that there are 44 slot squares even for planes that max out at 42 slots at Lv20 should have been a clue that they *could* go beyond Lv20 if they wanted to. I kinda hope they don't.