KUSA - This week marks 25 years since a flight from Denver to Chicago crashed in a corn field in Iowa.
On July 19, 1989, United Airlines Flight 232 had a catastrophic engine failure.
The crew tried to land at Sioux City's airport, but the failure of the fan disc in the tail engine destroyed all three of the plane's hydraulic lines.
The odds of that kind of failure were 1 in a billion.
Exactly 111 people on board were killed in the crash, but 184 survived. The crew is credited with using the remaining engines to lessen the impact.
9NEWS aviation expert Greg Feith spoke with our Marty Coniglio about the changes since then to prevent this kind of incident from happening again.
Watch the video above