German airlines are dropping safety rules brought in after the 2015 Germanwings plane crash which require two people in the cockpit at all times.
Andreas Lubitz killed 150 people by crashing the plane - apparently on purpose - after the plane's captain left to use the toilet.
Airlines now say the two-person rule has no safety benefits.
Eurowings, which merged with the Germanwings brand, is one of the airlines now dropping the requirement.
The German airline association BDL announced the change, which will come into effect by 1 June, on its website. It said its airlines will be re-introducing their original cockpit safety procedures.
The European Aviation Safety Agency, which was behind the original rule change, relaxed the requirements last year to allow individual airlines to evaluate their own safety needs.
BDL said that its airlines had "independently" reviewed the rules and decided that the two-person rule had no safety benefits - and could actually be more dangerous.
The group said the changes caused "more frequent and predictable" opening of the cockpit door and expanded the number of people with access to the cockpit.
It also said that the risk of a similar incident to the Germanwings crash was extremely low, and the risk of criminal or terrorist activity was much higher.
Lufthansa, the country's biggest airline, is one of the groups removing the requirement. Its airlines include Austrian Airlines, Swiss Airlines, and Eurowings - which was merged with Germanwings in 2015, a process which had begun before the company's high-profile crash.
However, other airlines in Europe have said they will be maintaining the two-person rule.
The investigation into the 2015 Germanwings crash found that co-pilot Lubitz locked the plane's captain out of the cockpit when he left to use the toilet, before putting the plane into a dive.
It struck the mountains at 700km/h (430mph) an hour, instantly killing everyone on board.
Investigators later discovered he had been suffering from psychiatric issues he had hidden from his colleagues. He believed he was losing his sight - although he was not - and had been taking psychotropic medication which made him unfit to fly.
Since the Germanwings crash, additional screening measures for mental health have been introduced for pilots.