The pilot is identified as Russell Hazelton of Factoryville, Pa. His wife, 69-year-old Suzanne Hazelton, is in critical condition.
The crash happened around 8:40 p.m. Wednesday. A witness said the Piper PA-28 Cherokee single-engine plane appeared to be attempting to land on the shore of the lake but instead ended up in the water, then flipped on its back.
The Federal Aviation Administration is investigating.
FAA spokeswoman Elizabeth Isham Cory says the plane took off from Delaware, Ohio, and was scheduled to land at Creve Coeur Airport, which is near the lake.