How unserviceable aircraft are authorised to make a ferry flight

Aircraft normally operate with a valid Certificate of Airworthiness (CofA) or, where applicable, a Restricted Certificate of Airworthiness. However, an aircraft may occasionally be unable to meet the conditions for a standard certificate while remaining capable of making a safe, controlled flight.

This may occur when an aircraft is being delivered to a new operator, positioned for maintenance, moved to storage, recovered after an incident, or flown for an inspection, test or modification. In such circumstances, the aircraft may be authorised to operate under a Permit to Fly (PtF), known in some regulatory systems as a special flight permit or ferry permit.

A Permit to Fly does not confirm that the aircraft is fully airworthy in the same way as an aircraft holding a normal CofA. It is an individual authorisation for a defined flight, subject to approved Flight Conditions that demonstrate how the aircraft can complete that flight safely. The applicable requirements should always be checked with the relevant EASA airworthiness framework or national authority.

What is a ferry flight?

A ferry flight is a positioning flight conducted for a specific purpose rather than for normal commercial or private operation. Typical examples include:

• Delivering an aircraft to a purchaser or new operator
• Flying an aircraft to a maintenance or repair facility
• Positioning an aircraft after a major inspection
• Moving an aircraft to a storage or preservation location
• Returning an aircraft to its State of Registry
• Conducting a post-maintenance or test flight
• Relocating an aircraft that cannot currently qualify for a standard Certificate of Airworthiness

Calling a flight a ferry flight does not, by itself, provide legal authority to operate. The aircraft must either retain a valid certificate and comply with its applicable requirements, or be issued with an appropriate Permit to Fly.

When is a Permit to Fly required?

An aircraft generally requires a Permit to Fly when it cannot be issued with, or can no longer retain, a valid Certificate of Airworthiness or Restricted Certificate of Airworthiness, but is nevertheless considered capable of safe flight under specified conditions.

Examples may include:

• An expired or unimplemented airworthiness directive
• A deferred defect that prevents compliance with the aircraft’s approved configuration
• An incomplete modification or repair
• An aircraft awaiting an inspection or maintenance action
• An aircraft undergoing a flight-test or development programme
• An aircraft that has not completed the requirements for a standard certificate
• An aircraft being recovered after damage or a prolonged period out of service

The assessment must relate to the proposed flight. It is not sufficient to state that the aircraft is generally safe enough. The applicant must identify the non-compliance, assess its effect, establish suitable operating limitations and demonstrate that the aircraft can safely perform the intended flight. For related guidance on defect management, see our article on how aircraft engineers defer defects using the MEL.

Who issues the Permit to Fly?

The process depends on the aircraft’s State of Registry and the applicable national or European regulations.

Under the EASA system, a Permit to Fly is generally issued by:

• The aviation authority of the Member State of Registry
• The authority designated by a Member State to prescribe identification marks for an unregistered aircraft
• An appropriately approved organisation that has been granted the relevant privilege

The European Union Aviation Safety Agency does not normally issue an individual Permit to Fly for a particular aircraft. Responsibility generally rests with the competent national authority or an organisation holding the required approval and privileges.

In the UK, the Civil Aviation Authority fulfils the relevant competent-authority role for UK-registered aircraft, subject to the applicable retained aviation regulations and approval arrangements. The CAA’s Permit to Fly guidance should be consulted for current application requirements.

An approved organisation may include:

• A Design Organisation Approval (DOA) holder
• A Production Organisation Approval (POA) holder, where permitted
• A Continuing Airworthiness Management Organisation (CAMO) or Combined Airworthiness Organisation, where its approval includes the relevant privilege

Not every approved organisation can issue a Permit to Fly. The organisation must hold the specific privilege, and its procedures, personnel, facilities and technical capability must cover the proposed flight.

The two-stage process: Flight Conditions and the Permit to Fly

A Permit to Fly is normally supported by approved Flight Conditions. These documents are central to the authorisation process.

1. Establishing the Flight Conditions

The Flight Conditions describe the circumstances in which the aircraft may safely fly. They normally address:

• The purpose of the flight
• The aircraft configuration
• The route and destination
• The permitted date or period of operation
• Weather limitations
• Maximum altitude and speed
• Required crew qualifications
• Required equipment
• Fuel and payload restrictions
• Take-off and landing limitations
• Emergency procedures
• Maintenance or inspection requirements
• Required ground support
• Applicable operational rules

The Flight Conditions should explain why the aircraft is capable of safe flight despite the identified non-compliance. They may impose restrictions such as daylight-only operation, visual meteorological conditions, no passengers, avoidance of congested areas or the presence of specialist personnel on board.

Where the applicable operational rules are not self-evident, the Flight Conditions should identify them expressly. A Permit to Fly does not automatically establish the complete operational framework for the flight.

2. Issuing the Permit to Fly

Once the Flight Conditions have been approved, the competent authority or appropriately approved organisation may issue the Permit to Fly.

The permit generally identifies:

• The aircraft registration or identification marks
• The authorised purpose of the flight
• The route or area of operation
• The validity period
• The approved Flight Conditions
• Any additional restrictions

A Permit to Fly is specific to the aircraft and the approved circumstances. It must not be treated as a general replacement for a Certificate of Airworthiness.

The importance of the Design Organisation’s technical scope

A DOA holder may have the privilege to approve Flight Conditions and issue Permits to Fly for certain ferry flights. Those privileges are limited by the organisation’s technical scope.

This distinction is critical. A DOA may hold the general privilege to approve Flight Conditions and issue a Permit to Fly, but it must also have the design capability to evaluate the technical issue affecting the aircraft. The relevant capability should be reflected in the organisation’s Terms of Approval.

For example, a DOA with the necessary privileges may be able to issue a Permit to Fly for an aircraft with an expired or unimplemented airworthiness directive. Before doing so, however, it must be capable of assessing the design aspects related to that directive and substantiating that the aircraft is capable of safe flight for the proposed ferry operation.

If the directive concerns avionics, a DOA without the avionics technical field in its Terms of Approval cannot approve the relevant Permit to Fly merely because it holds a general privilege to approve Flight Conditions and issue permits.

The organisation must have the expertise and approval scope necessary to assess the affected systems, structures, equipment or design data. Where appropriate, it may need to involve the type-certificate holder, supplemental type-certificate holder, a specialist design organisation or the competent authority.

Example: an overdue airworthiness directive

Consider an aircraft that is due to fly from an operator’s base to a maintenance organisation. An airworthiness directive affecting a flight-control component has passed its compliance deadline, so the aircraft no longer satisfies all the requirements for its normal Certificate of Airworthiness.

The aircraft may still be eligible for a Permit to Fly if:

• The effect of the overdue directive is clearly understood
• The affected component and associated systems are inspected or assessed
• The responsible organisation has the appropriate design capability
• The proposed route and operating conditions are evaluated
• Any necessary restrictions are included in the Flight Conditions
• The aircraft is shown to be capable of safe flight for the specific ferry operation
• The competent authority or appropriately approved organisation accepts the application and supporting data

The permit might restrict the aircraft to a short daylight flight, with no passengers, favourable weather, specified altitudes and direct routing to the approved maintenance facility.

This does not cancel the airworthiness directive or make the aircraft compliant. It authorises a limited flight before the required corrective action is completed.

What if the defect affects avionics?

Avionics defects can be particularly significant because they may affect:

• Navigation capability
• Communication systems
• Transponders and surveillance equipment
• Instrument flight capability
• Terrain-awareness systems
• Electronic flight instruments
• Automatic flight systems
• Flight-control computers
• Required warning or alerting systems

A DOA without the avionics technical field in its Terms of Approval cannot approve a ferry Permit to Fly for an overdue avionics airworthiness directive, even if it is otherwise authorised to approve Flight Conditions and issue permits.

The technical scope must match the issue being assessed. If it does not, the applicant must obtain the necessary evaluation from an organisation or authority with the required competence and approval coverage. Engineers dealing with electrical or avionics defects may also benefit from this guide to troubleshooting intermittent aircraft electrical faults.

Does a Permit to Fly make the aircraft fully legal to operate?

No. A Permit to Fly addresses the aircraft’s airworthiness status for the authorised flight. It does not automatically resolve every other regulatory requirement.

The operator may still need to consider:

• Flight crew licensing and qualifications
• Aircraft registration and identification
• Radio licensing
• Insurance
• Maintenance release or technical acceptance
• Operational approvals
• Noise requirements
• Dangerous goods restrictions
• Airspace requirements
• Airport permissions
• Customs and immigration requirements
• Overflight and landing permits
• Requirements imposed by other States

A Permit to Fly issued by one authority may not automatically be accepted by every country along the proposed route. The operator should confirm acceptance with each relevant State and obtain any required overflight or landing clearances before departure.

Ferry permits and operating rules

The flight must be conducted in accordance with the applicable operational regulations. A Permit to Fly does not automatically exempt the operator from normal operational requirements unless a specific exemption or alternative arrangement has been approved. In jurisdictions using a special flight permit framework, the FAA’s special flight permit information illustrates the importance of defined conditions and limitations.

The Flight Conditions should make clear:

• Which operational rules apply
• Which rules are modified or limited
• What weather minima must be used
• Whether passengers are prohibited
• What crew composition is required
• Whether the flight must remain in visual meteorological conditions
• Whether the aircraft may enter controlled or congested airspace
• What equipment must be serviceable
• Whether additional communications or escort arrangements are required

Where the rules are not self-evident, the Flight Conditions should state the applicable operational rules and conditions expressly. This prevents uncertainty for the operator, flight crew, air traffic service providers and authorities along the route.

Can an unserviceable aircraft carry passengers?

Usually, the purpose of a ferry Permit to Fly is to move the aircraft, not to conduct normal passenger operations. The Flight Conditions will commonly prohibit passengers or restrict carriage to essential crew and technical personnel.

Any person carried must be included in the approved conditions, and the safety justification must account for their presence. A permit must not be interpreted as permission to conduct ordinary commercial service unless the applicable authority has specifically approved that operation.

Who is responsible for the aircraft before departure?

Issuing a Permit to Fly does not remove the operator’s responsibility to ensure that the aircraft is prepared for the authorised flight.

Before departure, the operator and flight crew should verify that:

• The aircraft matches the configuration described in the Flight Conditions
• Required inspections and maintenance actions are complete
• No new defect invalidates the assessment
• Required equipment is serviceable
• Fuel, weight and balance limitations are satisfied
• Weather conditions are within the approved limits
• The route remains suitable
• All required permissions have been obtained
• The Permit to Fly and Flight Conditions are carried on board
• The crew understands every restriction and emergency procedure

If the aircraft changes configuration or develops an additional defect, the existing authorisation may no longer be valid. A revised assessment, amended Flight Conditions or a new permit may then be required.

Permit to Fly versus a normal Certificate of Airworthiness

• Certificate of Airworthiness: supports normal operation within the aircraft’s approved category and limitations. It assumes compliance with the applicable airworthiness requirements and is not normally limited to a single ferry route.
• Permit to Fly: authorises a specific flight or limited series of flights. It may be issued despite defined non-compliance, is supported by approved Flight Conditions and normally includes route, date, purpose and operating limitations.

A Permit to Fly is therefore a controlled exception, not a general alternative to maintaining the aircraft in an airworthy condition.

The role of the competent authority

The competent authority may:

• Review the application and supporting data
• Approve the Flight Conditions
• Issue the Permit to Fly
• Accept an approved organisation’s recommendation
• Impose additional restrictions
• Require inspections, tests or design substantiation
• Limit the route, weather, crew or aircraft configuration
• Refuse the authorisation if safe flight cannot be demonstrated

The authority’s involvement depends on the applicable rules and the privileges held by the organisation making the application. An approved DOA may be able to approve the Flight Conditions and issue the permit directly, but only within its approved procedures and technical scope.

Final considerations

An aircraft does not have to be compliant with every airworthiness requirement to make a ferry flight, but it must be shown to be capable of safe flight under defined conditions.

The authorisation normally depends on:

• Identifying why the aircraft cannot hold or retain a normal Certificate of Airworthiness
• Assessing the effect of that non-compliance
• Confirming that the responsible organisation has the necessary technical competence
• Preparing and approving suitable Flight Conditions
• Obtaining a Permit to Fly from the competent authority or an appropriately approved organisation
• Ensuring that the flight complies with the approved conditions and all applicable operational rules
• Obtaining acceptance and permissions from other States where required

The privileges of a DOA are never unlimited. They are linked to the organisation’s Terms of Approval and technical scope. A DOA may have the authority to issue a Permit to Fly in principle, but it must also be able to evaluate the specific design area affected by the aircraft’s non-compliance.

A ferry Permit to Fly is therefore a controlled safety authorisation. It allows an aircraft that cannot operate normally to complete a necessary positioning flight while ensuring that the route, aircraft condition, crew, operating environment and technical limitations have been considered and formally controlled.

Learn more about MEL defect deferral and explore the latest aviation maintenance articles from AeroTech Careers.