The number of air marshals on each plane is not something that is publicly disclosed, as it is considered to be sensitive security information. However, we can provide some general information about air marshals and their role in aviation security.

Air marshals are Federal law enforcement officers who are responsible for protecting the safety and security of commercial air travel. They are typically assigned to flights that are deemed to be at higher risk of terrorist activity or other threats, and their presence on a flight is meant to deter and respond to any potential security threats.
Air marshals are trained in a variety of tactics and techniques to help them identify and respond to potential threats, including surveillance and intelligence gathering, close-quarters combat, and the use of firearms. They also work closely with other law enforcement agencies and aviation security personnel to coordinate security measures and respond to any incidents that may occur.
The number of air marshals assigned to a particular flight depends on a variety of factors, including the perceived level of risk associated with the flight, the size and configuration of the aircraft, and other operational considerations. However, it is generally believed that there are usually at least one or two air marshals assigned to each high-risk flight.
It is important to note that the role of air marshals is just one part of a larger aviation security system that includes many other measures, such as passenger and baggage screening, secure cockpit doors, and other security protocols. While the presence of air marshals on a flight can help to deter and respond to security threats, it is not a guarantee of absolute security. It is important for all passengers and crew to remain vigilant and report any suspicious activity to authorities in order to maintain the safety and security of air travel.