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How did 911 hijackers get into cockpit?

On September 11, 2001, 19 terrorists associated with the Islamic extremist group al-Qaeda hijacked four airliners and carried out suicide attacks against targets in the United States. Two of the planes were flown into the twin towers of the World Trade Center in New York City, a third plane hit the Pentagon just outside Washington, D.C., and the fourth plane crashed in a field in Pennsylvania after passengers attempted to retake control.

The hijackers were able to gain access to the cockpits and take control of the planes by taking advantage of weaknesses in airport security as well as breaches in protocol by the airlines and flight crews. Their ability to seize the aircrafts allowed them to redirect the flights and crash them into their intended targets, causing immense loss of life and initiating dramatic changes to aviation security worldwide.

Boarding the Planes

The 19 hijackers booked early morning flights on September 11, 2001 in order to take advantage of lighter security before the day got busy. They chose flights from Boston, Washington D.C. and Newark that were bound for California. The flights were American Airlines Flight 11, United Airlines Flight 175, American Airlines Flight 77 and United Airlines Flight 93.

The hijackers were able to smuggle small knives and box cutters either in their carry-on luggage or on their persons. At the time, carry-on rules enforced by the Federal Aviation Administration allowed small knives with blades less than 4 inches. Airport security was more focused on finding explosives, rather than knives and cutters.

When passing through security checkpoints at their respective airports, some hijackers set off metal detector alarms but were then waved through after producing false IDs or being patted down improperly. Security cameras also recorded some hijackers having what appeared to be long discussions with ticket agents, which may have been efforts to gain more information about flight details and cockpit procedures.

Gaining Access to the Cockpit

Once onboard the aircraft, the hijackers waited until the planes were in flight before making their moves to gain access to the cockpits. This was approximately 30 minutes into each flight, when the aircraft had reached their cruising altitudes.

The hijackers initiated their takeovers by using their smuggled knives and box cutters to threaten or kill flight attendants and passengers near the front of the cabins. They reportedly sprayed chemical irritants to force passengers and crew to the back of the plane.

With the passengers and cabin crew incapacitated or subdued, the hijackers moved quickly towards the cockpits. On American Airlines Flight 11, hijackers stabbed two flight attendants, allowing them to gain access to the cockpit door. The door was opened, allowing the hijackers to enter the cockpit and take over the controls.

On the other three flights, the hijackers were able to force their way into the cockpits more quickly by exploiting breaches in security procedures:

  • United Airlines Flight 175 – A flight attendant was stabbed, and with the cabin crew threatened, a hijacker was able to enter an unlocked cockpit door.
  • American Airlines Flight 77 – Hijackers were able to enter through an unlocked cockpit door after threatening a flight attendant with a bomb.
  • United Airlines Flight 93 – After attacking passengers and crew, a hijacker was invited into the cockpit after claiming a bomb was onboard. Once inside, three more hijackers rushed in behind him.

Once inside the cockpits, the hijackers rapidly overpowered the pilots and took control of the flight controls. With access to the cockpits secured, they were able to redirect the flights toward the East Coast and their intended targets in New York and Washington D.C.

Airline Security Weaknesses Exploited

The relative ease with which the hijackers were able to breach the cockpits was enabled by weaknesses in the aviation security measures and procedures at the time:

  • Lax screening practices – Knives and box cutters were allowed on planes, and screeners were focused mostly on finding explosives or firearms.
  • Poorly designed cockpit doors – Cockpit doors were flimsy and could be broken down to gain entry.
  • Inadequate keypad door locks – Door locks were accessible by cabin crew and did not have adequate access codes.
  • Unenforced procedural lapses – Airlines failed to enforce procedures prohibiting access to unlocked doors.
  • Lack of air marshals – No trained and armed air marshals were on board the flights to respond to the threats.

These security gaps allowed the hijackers to smuggle in weapons, swiftly gain access to the cockpits, and seize control of the aircraft.

Cockpit Security Improvements Since 9/11

In the aftermath of the 9/11 attacks, aviation authorities took swift action to improve cockpit security and prevent hostile takeover of aircraft. Some of the major changes included:

  • Fortified cockpit doors – Cockpit doors were reinforced and bulletproofed to prevent forced entry.
  • Video monitors – Video monitors were installed so pilots could see the area outside the cockpit door.
  • Secure door locks – Keypad door locks were strengthened with secure access codes known only to the pilots.
  • Flight deck access procedures – Strict procedures were put in place governing opening/closing of cockpit doors during flights.
  • Increased air marshals – More armed and trained air marshals were deployed on U.S. flights.
  • Improved screening – Additional screening measures were added to prevent weapons smuggling onto planes.

These enhancements have been largely successful in protecting cockpit access and preventing hostile takeovers post-9/11. However, aviation security remains an evolving challenge requiring constant diligence and improvement.


The 9/11 hijackers were able to gain access to the cockpits and seize control of the four flights by exploiting weaknesses in aviation security in place at that time. Taking advantage of lax screening, unfortified cockpit doors, and breaches in protocol, they managed to smuggle in weapons and overwhelm the pilots, allowing them to redirect the planes toward their intended targets. The attacks led to major improvements in cockpit defenses and screening procedures that have heightened aircraft security and prevented further hostile takeovers of planes. However, continued vigilance and adaptation to emerging threats is essential to maintain the highest levels of aviation security.