A pilot has died in an ultralight plane crash in Sydney's southwest.

The Drifter plane hit the ground at Oakdale just before 4.30pm on Friday, a Civil Aviation Safety Authority spokesman told AAP.

Police said the man died as a result of the crash, which occurred about six kilometres from The Oaks Airfield.

The single-engine Drifter has open sides and can feature one or two seats, the CASA spokesman said.

AAP