How often do airline pilots find problems during preflight walk-arounds?

How many hours do most planes fly before a major overhaul? How long does it take to do a complete overhaul? Who does the overhaul: the airline, manufacturer or a subcontractor?

– Frank Kaminski, Cheswick, Pennsylvania

There is not an “average” time for airplanes between heavy maintenance due to the vastly different usage of airplanes. Some fly many cycles (take offs and landings) per day while others fly only a few. Some fly many hours on international routes while others fly a few hours at night and sit during the day.

My friends in maintenance tell me that they expect to see an airplane in heavy maintenance around every two years. 

The time planes spend in heavy maintenance can vary but they’re usually out of service for several weeks. 

As for who performs that heavy maintenance, the work is usually outsourced to a company that specializes in this type of work. They are located around the world, resulting in airplanes from many different countries being overhauled in many different locations.  In fact, it is very common for U.S. airplanes to be sent overseas for heavy maintenance. There are heavy maintenance facilities in Mexico and I have seen several U.S. airplanes in Hong Kong. 

There are a few heavy maintenance facilities in the U.S., such as in Tampa. But most airliners are sent overseas for maintenance.

A few airlines have their own heavy maintenance facilities such as San Francisco or Tulsa, but the number has decreased over the years. 

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems. The views and opinions expressed in this column are the author’s and do not necessarily reflect those of USA TODAY.

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