For about two years after March 2015, if you flew with almost any European airline and one of the pilots stepped out to use the lavatory, a flight attendant stepped in. They did not touch the controls. They simply stood or sat in the cockpit until the pilot came back, so that the flight deck was never occupied by a single person. This was the two-person cockpit rule, and it is one of the clearest examples of how a single accident can rewrite airline procedures across a whole continent within days.

It also shows how those procedures get reviewed once the shock has passed. Europe introduced the rule almost overnight after the loss of Germanwings Flight 9525, and later stepped back from making it mandatory. Here is what the rule is, why it exists, why many airlines dropped it, and what replaced it.

Why the Cockpit Door Became a Fortress

The rule only makes sense in the light of what came before it. After the attacks of 11 September 2001, airlines worldwide fitted reinforced, lockable cockpit doors. The aim was simple: nobody in the cabin should be able to force their way onto the flight deck. On the Airbus A320 family the door can be locked from inside, and the design deliberately lets the crew inside refuse entry, so that a hijacker cannot coerce a cabin crew member into opening it.

That design solves one problem extremely well. It also creates a rare but terrible failure mode: if the person who is alone in the cockpit is the threat, the people outside cannot get in.

CNN on how post-9/11 cockpit doors are designed to stop forced entry.

Germanwings Flight 9525

On 24 March 2015, Germanwings Flight 9525 was flying from Barcelona to Düsseldorf with 144 passengers and six crew on board the Airbus A320 D-AIPX. While the captain was out of the cockpit, the co-pilot locked the door and kept him out. The aircraft descended into the French Alps, and all 150 people on board were killed.

The French investigation agency BEA concluded that the co-pilot crashed the aircraft deliberately, and that he had been suffering from a mental illness that had not been reported to his employer or the aviation authorities. It recommended clearer rules on when doctors may share information about a patient who poses a risk to public safety.

Smithsonian Channel on the investigation into Germanwings Flight 9525.

Europe Adopts the Rule in Three Days

Airlines moved before regulators did. Within a day or two of the first findings, carriers including Lufthansa, easyJet, Norwegian and Air Canada announced that two crew members would be in the cockpit at all times. On 27 March 2015, the European Union Aviation Safety Agency issued a temporary recommendation that every airline should do the same, with at least two crew, including one qualified pilot, on the flight deck throughout the flight.

In practice, when one pilot left, a cabin crew member entered and stayed until the pilot returned. The cabin crew member was not there to fly. Their job was to be present, and to be able to open the door from inside.

In the United States the idea was not new. A similar practice, in which a flight attendant enters the cockpit when a pilot leaves, was already in force there before 2015, which is why American coverage of the change focused on Europe catching up.

KHON2 news report from March 2015 on the two-person practice on U.S. flights.

Why Europe Stepped Back

Once the immediate response was over, EASA reviewed the measure. The rule had costs of its own. The cockpit door had to be opened more often, which is exactly what the post-9/11 doors were designed to avoid, and the extra person on the flight deck also had to be someone the crew could trust.

In July 2016 EASA replaced its blanket recommendation with Safety Information Bulletin 2016-09, which asked each airline to assess its own risks first.

German airlines went further. In April 2017 the German Aviation Association, the BDL, announced that its members would end the mandatory rule by 1 June 2017, arguing that opening the door more often created a security risk of its own and that hijackings and criminal attacks were a far more common threat than a pilot acting alone. Airlines elsewhere in Europe made their own decisions, and some kept the procedure.

What Replaced It: Pilot Mental Fitness

The longer-lasting changes after Germanwings were about the people in the seats rather than the door. Europe updated its pilot medical requirements in 2016, and in 2018 adopted new operating rules that require European airlines to give pilots access to a support programme, to carry out a psychological assessment before a pilot starts flying for them, and to introduce alcohol testing of flight and cabin crew, with a two-year transition period.

Peer support programmes, run by fellow pilots, are designed to give a struggling pilot somewhere to turn before a problem becomes a safety issue, without automatically ending their career.

Why the Question Is Back in 2026

The debate over who is in the cockpit returned on 30 September 2026, when flydubai FZ1073 diverted to Tabuk in Saudi Arabia after one pilot attacked the other in flight. Passengers and crew subdued the assailant. The investigation is at an early stage, and we have set out what is established and what is not in our report on the FZ1073 co-pilot.

What the episode illustrates is the trade-off at the heart of the two-person rule: a locked cockpit door protects the pilots from the cabin, but it cannot protect a pilot from the person sitting next to them. Every airline policy on cockpit access is an attempt to balance those two risks.

Sources: EASA press release, 27 March 2015; EASA Safety Information Bulletin 2016-09, July 2016; EASA news release, 25 July 2018; BEA final report on Germanwings Flight 9525, March 2016; The Local and Associated Press, 28 April 2017; NPR, 27 March 2015; Wikipedia, Germanwings Flight 9525