Incidents like UA2005 are exactly why secondary cockpit barriers matter.
An Installed Physical Secondary Barrier (IPSB) is a lockable metal gate positioned between the passenger cabin and the cockpit. Its purpose is simple: provide an extra layer of security whenever the cockpit door must be opened during flight.
After 9/11, cockpit doors were heavily reinforced, but a vulnerability remained whenever pilots needed to briefly open the door for lavatory breaks, meal service, or crew changes. During those moments, the IPSB acts as a physical shield, preventing unauthorized access to the flight deck.
To be certified, the barrier must:
• Occupy enough space that it can't be bypassed by going over, under, or around it.
• Resist forceful intrusion attempts.
• Be quickly deployable and stowable by the crew.
• Remain stowed during taxi, takeoff, and landing.
The FAA mandated secondary cockpit barriers under 14 CFR 25.795, although implementation timelines have been adjusted over time. The barriers are now becoming a standard security feature on newly delivered airliners.
United Flight 2005 (ORD–MSP) diverted to Madison after an unruly passenger allegedly attempted to breach the cockpit while ranting in Russian.
Passengers reported the individual was removed in handcuffs as police swept the aircraft. Reports indicate authorities treated the incident as a possible hijacking attempt, with the FBI notified.
Level 4 security events involve an attempted or actual flight deck breach—the most serious category of onboard security threats.