During the 1990s, a series of issues affecting the rudder of Boeing 737 passenger aircraft resulted in multiple incidents. In two separate accidents, pilots lost control of their aircraft due to a sudden and unexpected rudder movement, and the resulting crashes killed everyone on board, 157 people in total. Similar rudder issues led to a temporary loss of control on at least one other Boeing 737 flight before the cause of the problem was ultimately identified.
N999UA, the aircraft involved in the accident, when still in service with Frontier Airlines
N221US, the aircraft involved in the incident, ten months before the incident
Wreckage of 9V-TRF, the Boeing 737-300 ivolved in the crash
United Airlines Flight 585
United Airlines Flight 585 was a scheduled passenger flight on March 3, 1991, from Denver to Colorado Springs, Colorado, carrying 20 passengers and 5 crew members on board. The plane experienced a rudder hardover while on final approach to runway 35 at Colorado Springs Municipal Airport, causing the plane to roll over and enter an uncontrolled dive. All 25 people on board the 737 were killed on impact.
N987UA, similar to the aircraft involved in the accident
N999UA, the aircraft involved in the accident, when still in service with Frontier Airlines