It is not necessarily forbidden toswap seats on an airplane, but there are some reasons why this may be discouraged or restricted. Airlines have specific policies and procedures that govern the distribution of passengers on board, and these rules are generally put in place for safety and comfort reasons.
One of the main reasons that airlines may discourage swapping seats has to do with security issues. During check-in, airlines allocate seats taking into account factors such as the weight and balance of the aircraft. They also ensure that passengers are placed in such a way as to facilitate evacuation in the event of an emergency. If passengers swap seats without informing the crew, it can upset this balance and make it more difficult in the event of an evacuation being necessary.
Additionally, crew members are trained to recognize passengers and their assigned locations. In the event of an emergency or situation requiring evacuation, it is important to be able to quickly locate each passenger on board. If passengers have swapped seats without informing the crew, this can cause delays and make it more difficult to implement emergency procedures.
When it comes to comfort, airlines may have specific policies regarding preferred seats, seats with more legroom, or seats near emergency exits. These seats can be assigned at an additional cost or reserved for passengers with specific needs. If passengers swap seats without permission, it can create problems and dissatisfaction among other passengers.
However, it is important to note that some airlines allow seat exchanges under certain conditions. For example, if you are traveling with a family member or travel companion and wish to be seated next to them, it is usually possible to ask the crew to make a seat change with the agreement of the persons concerned.
In summary, although it is not strictly forbidden to swap seats on board an aircraft, airlines have specific policies for reasons of safety, aircraft balance and passenger comfort. It is important to respect these rules and to consult the crew if you wish to make a change of seat.