The cockpit is the final point of defense against anyone who would want to take the airplane over. If we arm the pilots we insure that whoever makes it to the cockpit to do harm will meet with the pest possible defense we can provide. Also, once someone taking over the plane has disarmed everyone else or incapacitated them, whos left?
Yes, arming pilots would improve the security of airplanes, because anyone considering causing trouble on an airplane would know that there is a person with a weapon on board. Pilots would need careful screening for mental health issues and would need to be trained in proper use, but if those safeguards are put in place, arming pilots can give them security and send a powerful message that violence and terrorism are not tolerable.
Since 2001 there has been three major attempts at terrorist attacks, all of which have been unsuccessful.The security precautions we have today is already keeping us safe. Arming a pilot could become a disaster very fast. Bullets are capable of breaking through the sides of a plane, which would cause depressurization throughout the plane which is a big problem. The security right now is enough to prevent anything bad happening