Pilots are told how high or low to fly the plane

Question: How are flight altitudes determined?

— Submitted by reader Mario B. Easley, S.C.

Answer: The flight operator files a requested altitude, usually done by the flight dispatcher, based on performance and economics. Air-traffic control reviews the flight plan, checking for conflicts. They issue the cruising altitude based on the requested flight plan and other traffic. Pilots fly the altitude assigned by air-traffic control.

Q: Do different airlines fly at different altitudes on the same routes? — Kevin G, San Diego

A: No, altitude is not based on the airline. Assigning altitude is firstcome, first-served.

Q: Under clear sky conditions, how far can you see at cruise altitudes?

— Jim Rogers, Fort Lauderdale

A: On a very clear day, the horizon at 35,000 feet is more than 200 miles.

Q: When a plane descends from the high-altitude jetway system to below 18,000 feet, what rules govern the path it is supposed to fly to get into either the low-altitude airway system or else to a low-altitude entry point to a STAR arrival?

— Bob in Massachusetts

A: In the U.S., the airplane is under positive radar control by air-traffic control, and the transition to the arrival route is part of the flight plan. If a deviation is necessary, air-traffic control will provide the appropriate clearance. Outside the U.S., or in case of no radar coverage, the flight plan contains the appropriate low-altitude airways, or more likely the transition to the Standard Terminal Arrival Route.

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