What is the primary action to take if a hijacking occurs before take-off?

The primary action to take if a hijacking occurs before take-off is to keep the aircraft on the ground. This action is critical because the safety of passengers and crew is the foremost priority in such situations. Keeping the aircraft stationary helps to limit the hijackers' options and maintain a level of control over the situation. It also allows law enforcement and security personnel to respond effectively, ensuring that they can manage the incident with the necessary resources and strategies.

In contrast, contacting ground control immediately is a necessary step but comes after ensuring the aircraft remains on the ground. Attempting to negotiate with hijackers poses significant risks to the safety of everyone on board and is generally not advised without proper training or backup from authorities. Evacuating passengers can lead to chaos and confusion, potentially putting them in greater danger. Therefore, maintaining control of the situation by keeping the aircraft grounded is the appropriate and safest primary action.