Ask the Captain: How often do commercial aircraft go in for maintenance?

What would you do if you had to quarantine your plane midair because someone has coronavirus?

– Mark 13:11, Wisconsin

If a person becomes ill on a flight, crews are trained to provide first aid. Additionally, many airlines have a medical specialist available via phone or radio patch.

If the passenger is ill and needs more medical attention, the captain can decide to divert.

If there is a question about a contagious disease, then the medical professionals at the diversion airport would have to determine if a quarantine were necessary.

I've noticed that a plane will arrive, deplane, board and then take off again. How long does a plane go at this pace before a scheduled maintenance check on the engines and other systems?

– Nathaniel, Atlanta

Modern airliners are very reliable, robust machines, logging thousands of hours in the air each year, though the number varies by operator.

For the sake of cost efficiency, most airlines do progressive maintenance which minimizes the downtime. At least every two days, line maintenance teams perform a visual check, fluid level check and tire pressure check. This “daily check” also provides the mechanics with a good opportunity to look for system abnormalities.

Every few days, the airplane is scheduled to spend time at a maintenance base, undergoing part of a more thorough maintenance examination.

Every couple of years, the airplane is taken out of service for what's called a "heavy" maintenance check. During this process, nearly all access panels are opened and parts of the plane – including the interior – are removed for closer inspection. Any corrosion is repaired and many other tasks are accomplished. After passing the heavy checklist, the airplane is again ready to fly several thousand hours per year.

Airlines have spent years and millions of dollars to create this progressive maintenance system and it works, very, very well. It extends the aircraft's service life by decades and keeps even older airplanes in very good shape. In fact, most older airplanes are retired for fuel-efficiency reasons, not because they're worn out.

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.

This article originally appeared on USA TODAY: Ask the Captain: How often do commercial planes undergo maintenance?