Conversation so far:
what is known about Alan Kulwicki's death?
Kulwicki died in an airplane crash on Thursday April 1, 1993.
where was Alan Kulwicki going when he died in a plane crash?
He was returning from an appearance at the Knoxville Hooters on the Kingston Pike, on a short flight across Tennessee before the Sunday spring race at Bristol.
how old was Alan Kulwicki when he died?
Died April 1, 1993 (aged 38)
what else is known about Alan Kulwicki's death?
The plane slowed and crashed just before final approach at Tri-Cities Regional Airport.
who else was in the plane with Alan Kulwicki when he died?
All four people on board, including two executives of the Hooters restaurant chain, were killed.

Question: what was the cause of the crash?
Self-contained rewrite: what was the cause of the airplane crash that killed Alan Kulwicki?