Most airline crews include two pilots, a captain and co-pilot. Together, they plan the course of the flight, check the operation of the plane and operate the plane. They also may test aircraft, fight fires from the air and rescue and evacuate injured persons.

SALARY: Salaries vary significantly with the size and success of an airline. Average starting, from $13,000 to $27,900. Experienced pilots average between $37,500 to $81,000.

EDUCATION: A bachelor's degree is prefered; a good number of pilots hold master's degrees. A pilot must have a commercial pilot license with an instrument rating from the Federal Aviation Administration. Many come from the military. Training is ongoing.

Air traffic controllers are responsible for the flow of traffic at an airport. They give pilots landing and takeoff directions, clear them for both and give flight advice based on weather and navigational reports from around the country. They make sure planes are a safe distance apart. They work at airports, air route traffic control centers and flight service stations.

SALARY: Starting base pay, $23,634.

EDUCATION: Applicants must pass a Civil Service exam and a physical. They must have three years of work experience, general or specific, or four years of college or a combination of education or experience totaling three years.

Corrections officers are responsible for the security of prisoners and the public. They guard those who have been arrested or those who have been convicted of crimes. They may work in county jails or state prisons. They monitor all daily activities, including work details and outdoor activities.

SALARY: Starting salaries for state officers average just above $19,000 a year; professional salaries averaged $22,900.

EDUCATION: Officers must be at least 18 and have a high school education. In Massachusetts, officers are chosen based on Civil Service exam scores. Credit is given for additional education. Across the nation, post-secondary education is increasingly preferred.

Every day, firefighters work to save property and lives. They ride speeding trucks to burning buildings, climb ladders and work as a team to put out fires. They also assist in medical emergencies, where they tend to injured or ill people. They must care for their equipment and continually update their training. They also help educate the public about fire prevention.

SALARY: Starting weekly base pay in Boston, $640.91; after 25 years, base pay is $860.30.

EDUCATION: Training is provided on the job at a firefighting academy. Aspiring firefighters must pass a written and physical exam and a strength test.

The all-volunteer Armed Forces protect and defend the country. Each branch has its own mission: the Army organizes land-based defenses, the Air Force readies for air and space defenses and the Navy prepares for sea defenses. The Marine Corps prepares for land movements in support of naval operations. The Coast Guard is the prime maritime authority in the United States; except in wartime, it operates as part of the Department of Transportation. The Armed Forces include a broad spectrum of job opportunities _ more than 2,000 for enlisted personnel and 1,600 for officers.

SALARY: Basic monthly pay for a recruit (E-1) is $790.20. Military personnel receive free room and board (or an allowance). The average military person makes $29,300 a year.

EDUCATION: A high school diploma is strongly preferred and required for some enlistment options. All recruits must be at least 17 (with parental consent) and be citizens or permanent resident aliens. Aspiring officers earn college degrees at the country's military academies or through ROTC programs at other colleges. They may also attend Officer Candidate School while in the military.

Police officers protect the public and enforce the law. They investigate crimes, apprehend suspected criminals and testify in court. They control traffic and get help for accident victims. They may give first aid to injured or ill people. They also do community relations and crime prevention work.

SALARY: Beginning Massachusetts state trooper, $31,140; national median salary for police and detectives, $34,000.

EDUCATION: A high school education is usually required; in some departments around the country, some college is demanded. Training is provided on the job for instance, at the State Police Academy. Applicants for many departments, such as Boston and the MBTA, must take the Civil Service exam. Aspiring state troopers must pass a different written exam. Recruits need a high school education and college training is encouraged.

DEMAND: While demand for police protection is growing, so is the demand for less government spending. Competition for jobs will be keen, especially at the federal level.