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28 October 2009

Airline Safety and Aging Aircraft - Why Flying in an Older Plane May Not Be Unsafe

As part of the's ongoing effort to show you what goes on behind the scenes, this article highlights one of the many questions that Dr. Curtis and get asked about various airline safety issues. The following questions were asked of Dr. Curtis by a travel magazine in August 2009. We hope that the questions and the answers address some of your concerns as well.

Question 1
Would it be accurate to say that it's hard to imagine that planes get safer as they age?

Thanks for taking the time to write to me. As for your questions, the first one is a bit more involved than it would first seem. To make a long story short, as a plane gets older, specifically the kinds of aircraft that are used in airline service in the US, Canada, and other countries with a similar high level or regulatory requirements, it becomes more expensive to maintain and to keep an aircraft in airline
operations. Part of this is due to the normal wear and tear that any complex machine would face with regular use. Part of it is also due to evolving requirements.

Over time, the number of requirements for airliners tend to go up rather than down, and some of these changes may require a retrofit of an aircraft. Depending on the change, it could be much more expensive to change an existing aircraft than it would be to incorporate changes into new aircraft.

On the one hand, over time an older airliner aircraft will likely face fewer risks because changing requirements, plus the collective experience of the aviation community, tend to reduce the likelihood of some dangerous conditions as well as reduce the potential for physical risks faced by passengers and crew. On the other hand, newer aircraft designs would in most cases already have the changes incorporated into the design and may have additional changes that were not mandated by the authorities but may have been included by the manufacturers because those changes makes the aircraft easier or cheaper to operate while at the same time reducing the likelihood of conditions that could lead to accidents.

If an aircraft is flying in a country with weak or nonexistent regulatory oversight, older aircraft will likely not have the kinds of changes and improvements that would be required in places such as the US, Japan, Australia, or the EU, and would likely be more of a risk than a newer aircraft flying in the same country.

Question 2
We're also curious about how old a plane can get in the U.S. before the FAA or DOT believes it is at an increased likelihood of being unsafe - do you have any idea on when this is?

Your second question is also not as easy to answer as it may seem. In short, there is no FAA age limit for airplanes. So long as the the aircraft operator is following the proper regulations and procedures and the airplane has been properly maintained and has passed the appropriate inspections, an airline can fly a plane of any age.

As far as whether the FAA thinks that older aircraft have an increased likelihood of being unsafe, I can't say. I am unaware of any study or document from the FAA that identifies any direct relationship between the age of an individual aircraft and the likelihood of a particular aircraft model being in an accident. There are however many FAA, DOT, and NTSB resources that provide historical details on accidents, accident rates, and certain other safety related events associated with an airline or aircraft model.

Related Resources
Top Ten Airline Safety Questions
Top 10 Airline Safety Tips


  1. Wire aging is one of the most serious concerns facing older commercial and military aircraft. No easy mechanism or procedures presently exist to do a 100% check of aircraft wiring, airlines can only spot-check wiring in accessible areas of the aircraft, perhaps leaving as much as 60% to chance. At an industry wire aging conference it was pointed out that every day there are 15 to 20 incidents where US commercial aircraft, in-flight or on-ground, have to be grounded because of wire aging related situations.

  2. typically wires don't age, it is the connectors and the way wire are attached/connected to the contcats of connectors/plugs, which does pose problems,i.e. vibrations may cause wires to break inisde connectors.........

  3. More than the wires themselves and even the connectors, the insulation and coating of the wires get degraded. Thgis result in leakage of electormagnetif fields. In extreme cases this fulx fields can interfare with signal transmission and cause wrong indications. Therefore old aircraft wiring and insulation on them make them susceptible.

  4. I thought there was a thing called metal fatigue and that it accured at an almost specific time that could be measured and therefore you would know when to pull a plane out of duty or was the movie all wet