LAKEVIEW, S.D. (AP) — The National Transportation Safety Board says a South Dakota pilot who died in a single-engine plane crash along with his teenage son should not have had a passenger.

According to a preliminary NTSB report, 39-year-old Clint VanderWey was certified only as a student pilot. Under federal aviation regulations, VanderWey was prohibited from being a pilot in command of a plane carrying a passenger.

VanderWey and his 16-year-old son, Jed, were killed Sept. 8th when their Cessna 140 crashed in a prairie near the family’s farm near Nebraska.

The NTSB says VanderWey took off from his private airstrip. Family members said VanderWey, who ran an irrigation service, would fly over water towers to report the water level to farmers.

The preliminary report found no mechanical problems with the plane before the crash.