LAKE WALES, Fla. -- Poor flight planning caused a mosquito control plane crash that killed two pilots performing relief operations for Hurricane Charley last year, federal officials said.

Pilot Dave Wilkes and co-pilot Harold Miller died when their twin-engine Piper Aztec hit an unlit 530-foot communications tower on Sept. 11, 2004.

The National Transportation Safety Board said the accident was caused by "the pilot's inadequate preflight planning and preparation, and his inadequate visual lookout."

The NTSB report, released recently, noted the tower's warning lights were off, but said pilots were warned of power outages in the area.

No mechanical problems were reported by the pilot or discovered during examination of the airplane after the accident.

Wilkes, 55, of Cleveland, Miss., and Miller, 53, of Sandwich, Ill., were employed by Vector Disease Control Inc., a Mississippi company contracted by the Federal Emergency Management Agency to spray for mosquitoes after last year's hurricanes.

They had taken off from Lake Wales Airport, about 45 miles south of Orlando, at about 4:15 a.m.