TMZ-Copeland negotiates dismissal of battery charge against Lohan ex

Michael Lohan's Achilles' Heel, Kate Major, will NOT be prosecuted for battering a passenger on a Delta flight ... TMZ has learned.

Sources tell us ... the L.A. City Attorney had a meeting with Kate's lawyer, Trent Copeland, today and prosecutors decided not to file the case. We're told the City Attorney was impressed that Kate was trying to solve her problem by checking into rehab. Copeland also made it clear ... Kate was apologetic for her conduct.

As we first reported, Kate was arrested and escorted off a flight from LAX to Tampa after accosting another passenger in first class. We're told Kate was drunk.

And get this ... Kate was on her way to Tampa, because she had a court date over a restraining order she sought against Michael Lohan for allegedly beating her up.