On October 31, 1994, the ATR 72 performing this route flew into severe icing conditions, lost control and crashed into a field, killing all 68 people on board in the high-speed impact.

National Weather Service reports revealed low cloud ceilings and visibility under three miles (five kilometers) in the area.

At 15:09:22, the pilot of a Beech Baron, N7983B, provided a pilot report (PIREP) to the DNV controller that there was "light icing" at 12,000 feet (3,658 m) over Lafayette, and, 22 seconds later, added that the icing was "trace rime...." According to the DNV controller, because the crew of flight 4184 was on the frequency and had established radio contact, the PIREP was not repeated.

At 15:18:07, shortly after flight 4184 leveled off at 10,000 feet, the BOONE controller notified the crew that they were cleared to the LUCIT intersection and gave their holding pattern, telling them to expect further clearance (EFC) at 15:30.

About half a second later, the ailerons rapidly deflected to 13.43 degrees right wing down (maximum designed aileron deflection is 14 degrees in either direction from neutral), the autopilot disconnected, and the CVR recorded the sounds of the autopilot disconnect warning (a repetitive triple chirp that is manually silenced by the pilot).

The captain's nose-up control column force exceeded 22 pounds, and the airplane rolled rapidly to the right, at a rate in excess of 50 degrees per second, bringing the plane completely inverted.

After the aircraft completed a full right roll and passed through a wings-level attitude, the captain said "alright man" and the first officer's nose-up control column force decreased below 22 pounds.

At 15:57:55, the normal acceleration increased to over 3.0 G, the sound of the ground proximity warning system (GPWS) alert was recorded on the CVR, and the captain's nose-up control column force again exceeded 22 pounds.

Approximately 1.7 seconds later, as the altitude decreased through 1,700 feet (518 m), the first officer made an expletive comment, the elevator position and vertical acceleration began to increase rapidly, and the CVR recorded a loud "crunching" sound.

The last recorded data on the FDR occurred at an altitude of 1,682 feet (513 m) (vertical speed of approximately 500 feet per second [150 m/s]), and indicated that the airplane was at an indicated airspeed of 375 knots (432 mph; 694 km/h), a pitch attitude of 38 degrees nose down with 5 degrees of nose-up elevator, and was experiencing a vertical acceleration of 3.6 G. The CVR continued to record the loud crunching sound for an additional 0.4 seconds.

The airplane impacted a wet soybean field in Lincoln Township, Newton County, Indiana, partially inverted, in a nose down, left-wing-low attitude.

The NTSB determined that the accident was not survivable because the impact forces exceeded human tolerances, and no occupiable space remained intact.

[1] The distribution of wreckage, combined with data from the flight recorders, indicated that the horizontal stabilizer and outboard sections of both wings separated from the airplane prior to impact, "in close proximity to the ground."

The unabridged NTSB probable cause statement reads: 3.2 Probable Cause The National Transportation Safety Board determines that the probable causes of this accident were the loss of control, attributed to a sudden and unexpected aileron hinge moment reversal that occurred after a ridge of ice accreted beyond the deice boots because: 1) ATR failed to completely disclose to operators, and incorporate in the ATR 72 airplane flight manual, flightcrew operating manual and flightcrew training programs, adequate information concerning previously known effects of freezing precipitation on the stability and control characteristics, autopilot and related operational procedures when the ATR 72 was operated in such conditions; 2) the French Directorate General for Civil Aviation's (DGAC's) inadequate oversight of the ATR 42 and 72, and its failure to take the necessary corrective action to ensure continued airworthiness in icing conditions; and 3) the DGAC's failure to provide the FAA with timely airworthiness information developed from previous ATR incidents and accidents in icing conditions, as specified under the Bilateral Airworthiness Agreement and Annex 8 of the International Civil Aviation Organization.

[1]: 210 The French Bureau of Enquiry and Analysis for Civil Aviation Safety (BEA) conducted its own separate investigation and agreed with the NTSB's cause of the accident as aileron deflection leading to loss of control.

However, the BEA stated in its response to the NTSB's report that the aileron deflection was caused by pilot error instead of by ice, citing several off-topic conversations made by the crew during the holding phase as well as the flight crew's extension of the flaps to 15 degrees while at a high speed, which can create large axial loads.

The NTSB stated that the crew's conversation took place at a non-critical moment of the flight and that the pilots were aware of the ice on the wings.

[citation needed] In March 1995, some families of the victims discovered remains of their loved ones at the accident site, giving rise to a suspicion that cleanup efforts were not thorough.

[6] In April 1996, the FAA issued 18 Airworthiness Directives (ADs) affecting 29 turboprop aircraft having the combination of unpowered flight controls, pneumatic deicing boots and NACA "five-digit sharp-stall" airfoils.

[citation needed] In the years following the accident, AMR stopped flying its American Eagle ATRs out of its northern hubs and moved them to its southern and Caribbean hubs at Dallas/Fort Worth International Airport, Miami, Florida, and San Juan, Puerto Rico, to reduce potential icing problems in the future.

In theory, that should solve the problem of the tendency of ice ridge formation at the 9% chord position of those obsolete sharp-stall airfoils.

[9] UTair Flight 120 crashed on April 2, 2012, because of a failure to deice the aircraft prior to takeoff, and 33 of the 43 people on board were killed.