RIVERSIDE -- The nation's largest firefighting aircraft will return to duty next week following repairs to a wing that was damaged after a near-crash.

The DC-10 air tanker had been out of commission since June 25 as it prepared to drop fire retardant along a Kern County ridge. A severe downdraft forced the aircraft to sink and its left wing clipped several treetops.

"We're thankful that no one got hurt and the damage was as minimal as it was," said Rick Hatton, managing partner of the company that owns the DC-10. "It's a testament to the robustness of the airplane."

The converted plane was hailed by California fire officials last year as the first jumbo fire bomber of its kind to battle wildland fires. The U.S. Forest Service has refused to certify the plane over concerns about the number of hours already logged on the 31-year-old DC-10.

A preliminary report by the National Transportation Safety Board last week said the aircraft's left wing dropped downward while making a left turn.

The cause of the accident is still unknown. The pilots have said they experienced air turbulence just before hitting the trees.