How does an aircraft fail to be airworthy?

If you are a follower of this site, and regularly read the comments, you might remember a comment from a few months ago talking about how this man’s aircraft (Cessna Citation Mustang) had been considered unairworthy. I too sat there and thought “How does this happen, how exactly does an aircraft fail to be airworthy?”

So I reached out to the commenter, who’s called Gary, and I asked him if he could explain this to me. I have owned and flown countless aircraft over the years, and my aircraft have always passed their 4 year inspections.

Now, I am not an aircraft technician, so I don’t know the exact rules and regulations. I just pay a technician to come to the airport, inspect my aircraft, and tell me if it has passed or failed.

So, Gary and I talked about his old Cessna Citation Mustang. He told me the reason it was not considered to be airworthy anymore was due to cracked avionics (essentially, the glass on some of his avionics in his aircraft were broken). It also transpired that Gary was an aircraft technician, so I asked him, what exactly would stop an aircraft from being airworthy.


What could mean that an aircraft isn’t considered to be airworthy anymore?

Cracked or inaccurate avionics, avionics are essentially all the electronic tools an aircraft uses. This can be things such as the navigation, radio, collision avoidance systems, fuel systems and so on. Obviously, this is a major safety problem.

If an aircraft’s avionics are inaccurate, it could mean bad news for the pilot of the aircraft. If the avionics are cracked, there could also be a problem with descending.

When the aircraft is descending, the pressure is different. This creates stress on the crack, and after a long time, with repeated exposure, the glass (which make up either the screen or the protector for most avionics) will shatter. This again causes safety issues, and would make it so the aircraft would fail to be airworthy.

Maintenance, this is key for any vehicle, whether it is a boat, aircraft or car, you need to keep your aircraft well maintained.

This is a major safety point for a pilot. If the aircraft is not properly maintained, it could become a hazard, not just to the pilot and the aircraft, but also anyone (or anything) near where the pilot is flying.

An ill-maintained aircraft may have parts missing, or certain parts of the aircraft that aren’t working at 100%. It is recommended that you maintain your aircraft after each and every flight in order to prevent this.

Maintenance is a big problem in the aviation industry, and can lead to certain airlines being banned in certain regions if they have a poor enough record.



Not having an airframe restoration, for a little Cessna, you probably don’t have to worry about doing this too much, only every 3000 flying hours (although it does vary per aircraft).

If your aircraft is over the 3000 flying hours mark and you have not had a restoration, it is serious grounds for your aircraft failing to be airworthy.

Again, this comes down to safety. When an aircraft is flying, no matter how high or how low, it is exposed to different stresses, on both the wings and the fuselage.

These stresses cause damage to the airframe, which over time, if left unrestored, can cause severe damage to the aircraft. An airframe restoration essentially repairs the damage done by the stress, on both the fuselage and wings.

Not having an engine overhaul, this is essentially the same as the airframe restoration. When flying, teh engine too is exposed to all the little grime, dirt and dust in our atmosphere, as well as the stresses that also affect the airframe. If left, and no overhaul is done, the aircraft can become seriously dangerous to the pilot.

This is because the engine ends up with a deposit of dirt and grime, which, if left to build up, will eventually corrode the inside of the engine, as they trap moisture.

If the engine has not been removed from the aircraft, cleaned and restored it will lead to the aircraft fail to be airworthy.

Not having a type certificate, each aircraft that is allowed to fly is granted a type certificate.

This is then given to each individual aircraft of that type of aircraft. It is imperative that each individual aircraft can present their type certificate to regulators, technicians and air traffic control if necessary.

Gary gave an interesting anecdote about type certificates: “If I ever get an aircraft that doesn’t have a type certificate, I just walk off and get back in my van, turn the engine on, and drive off.

It’s not that I don’t want to work on that amazing aircraft- trust me, I really do, it’s that I’m legally not allowed to work on that aircraft. Although, it is quite funny to see the owner’s face when I just drive off, but that does make me sound a little rude.”

No valid registration markings, just like cars, aircraft need to have registrations. On a car, this is done through number plates, which tell you where the car was registered, when it was registered, and a few other identifying features.

The same is said for aircraft, although, the aircraft has a marking on the side of the aircraft, on the tail, or on the engines.

If an aircraft does not have these, so that they are visible to ground crew, it is considered illegal, and the aircraft will often be refused passage to most airports and/or reported to the local aviation authority.

Due to the legality (or illegality) surrounding the issue, any aircraft without registration markings will fail to be airworthy, and won’t be allowed to fly.



No valid flight manual, if there is no valid flight manual, that means there are no logs for the aircraft. This is an essential piece of equipment when it comes to determining how airworthy an aircraft is.

This is because the aircraft needs to have both a digital and physical flight log, so that regulators can see how often that particular aircraft has flown in a given time.

This is also used as an indicator as to how much fatigue and stress there should be on the haul of the aircraft.

Most technicians aren’t obligated to look at this (although it varies from country to country), but many do, as it tells them what they can expect to see when looking to certify the aircraft as airworthy or not.

Have you ever had an aircraft that failed to be airworthy? What was the reason? Tell me in the comments!