NSW light plane crash victims on the mend

The condition of a man and woman critically injured in a light plane crash southwest of Sydney has improved.

The 24-year-old pilot and his female passenger, 23, were taking off from Camden Airport on Thursday morning when their hired plane suffered suspected engine failure and crash-landed into a paddock.

The pair, who were taken to Liverpool Hospital in a critical condition with facial, head and limb injuries, are now in a stable condition, a hospital spokeswoman told AAP on Friday.

Engine failure will be the focus of investigations about the crash, which occurred in a residential area in Kirkham.

The pair had hired the single-engine 1977 Piper plane for a one-hour private sightseeing flight.