The writer, producer and director died early Tuesday morning at his home in Santa Monica ... according to his son, Joseph.

We're told Jim had been battling leukemia for 20 years, and the cancer was a contributing factor in his death. His son says Jim was in remission at one point during his cancer battle, but the disease came back and he was always battling the cancer.

Jim, we're told, was surrounded by family when he died.

JA is best known for writing, directing and producing "Airplane" with Jerry and David Zucker ... the comedy filmmaking trio met in college at the University of Wisconsin-Madison and started a comedy group, Kentucky Fried Theater, leading to their popular screwball comedy flicks.

Jim also worked on the "Police Squad!" TV series and the 'Naked Gun' franchise with Leslie Nielsen ... and he also lent his comedic genius to "Top Secret!" and "Hot Shots!"

David Zucker tells TMZ ... he and Jerry visited Jim at his home Monday night, and he was already unconscious. They held his hand and told him how much they loved him and are very sad about his passing. David also adds, "Jerry and I are heartbroken, but at least Jim won’t ever have to see Naked Gun 4"

Jim was 80.