In modern aviation, a First Officer (FO) not only can but is legally and professionally obligated to take control of the aircraft from the Captain if they believe the safety of the flight is at risk and the Captain is not responding to warnings. This is a core principle of Crew Resource Management (CRM). If the Captain becomes incapacitated or is making a dangerous error (like flying toward terrain) and fails to correct it after several verbal prompts, the First Officer will clearly announce, "I have control" (or "My aircraft"). On Boeing aircraft, the control columns are physically linked, so the FO can physically override the Captain's inputs; on Airbus aircraft, there is a "Priority Takeover" button on the side-stick that allows one pilot to electronically deactivate the other's stick. Historically, many accidents occurred because junior pilots were too intimidated to challenge a senior Captain, so modern training emphasizes that the person "monitoring" the flight has just as much responsibility for safety as the person "flying" it.