Permit aviation is the gateway to lower cost flying. The key feature is that the pilot/owner of permit type aircraft takes full legal responsibility for the airworthiness of their aircraft and in return can do far more of their own maintenance, even building the aircraft from scratch or restoring an un-airworthy aircraft.
More than any other field of human endeavour, safety has always been the paramount concern in aviation. As a result, a worldwide system has developed which offers pilots, passengers and people on the ground, assurance as to the safety of every individual aircraft. This system of regulations will not allow any aircraft to be flown without some assurance as to its fundamental safety.
The better-known part of this system results in what is called a "certificate of airworthiness" (CofA). Aircraft bearing this document are sold and supported by approved manufacturers, including well known brands such as Piper and Cessna, who bear legal liability for the safety of their aircraft design and manufacture. Such aircraft must also be professionally maintained to remain in strict adherence to the manufacturers specifications. Only pre-approved and tested modifications and upgrades can be performed. On the other hand, CofA aircraft can fly in any territory around the world.
In contrast, the less well-known equivalent to a CofA is a "Permit to Fly". A permit is a fundamentally different 'contract' between the governments who issued them and the pilot/owners to whom they are issued. The current owner is the 'manufacturer' of their permit aircraft and they assume all of the responsibility that would be borne by the original manufacturer in the case of a CofA aircraft. This is the system used by designers of amateur homebuilt aircraft who sell construction plans and also the manufacturers of kits for homebuilt aircraft
It is also common for aircraft that formerly held a CofA to become permit aircraft. This can happen when a manufacturer goes out of business and nobody takes over the "type certificate" (the document that encapsulates their responsibility for keeping the design current). Equally, manufacturers can sometimes chose to extinguish the type certificate for an obsolete design. All of the aircraft that formerly held such a CofA then become 'orphaned'. Their owners then have to seek a permit to fly in order to continue using their aircraft. Many attractive 'orphaned' classic and vintage types continue to fly as permit aircraft. Even non-flying distressed and damaged aircraft of these types are restored and returned to flight under a permit.
While a permit system would obviously not be suitable for large transport category aircraft, it is more than adequate for leisure aviation in light aircraft. Over time, experience has shown that the risks are small and the aircraft are generally operated very safely. Consequently the freedoms extended to permit aircraft have tended to increase.
There are many freedoms and benefits of permit aviation over Certified flying:
On the other hand, there are some additional limitations on permit aircraft compared to CofA types: