A certificate of release to service (CRS) is the signed statement that closes a maintenance job. With it, authorised certifying staff confirm that the ordered work was done in accordance with approved data and the organisation's procedures, and that the aircraft or component can return to service for that work. Under EASA it is required by point 145.A.50 of Part-145. The FAA equivalent is the approval for return to service in the maintenance record under 14 CFR part 43, and FAA Form 8130-3 for components.
What a CRS is, and what it is not
The basic rule is in 145.A.50 of the EASA Easy Access Rules for Continuing Airworthiness (Regulation (EU) No 1321/2014, Annex II, as amended by Regulation (EU) 2021/1963). In summary:
- 145.A.50(a): the CRS is issued by appropriately authorised certifying staff on behalf of the organisation. They issue it when they have verified that all ordered maintenance was properly carried out under the procedures of 145.A.70, using the maintenance data of 145.A.45, and that there are no known non-compliances which endanger flight safety.
- 145.A.50(b): a CRS must be issued before flight at the completion of any maintenance.
- 145.A.50(c): new defects or incomplete work orders must be reported to the person or organisation responsible for the aircraft's continuing airworthiness, to agree whether they are rectified.
- 145.A.50(e): if the organisation cannot complete all ordered maintenance, it may issue a CRS within the approved aircraft limitations, and it must record that fact in the CRS.
EASA guidance also says what a CRS does not mean. GM1 145.A.50(a) explains that a CRS certifies the work agreed in the work order or contract. For aircraft maintenance, it "does not necessarily mean that the aircraft is in airworthy condition". Airworthiness before each flight remains the responsibility of whoever manages the aircraft's continuing airworthiness, usually the operator's CAMO. The same GM states that an overdue airworthiness directive is considered a hazard to flight safety.
Part-M (M.A.801), Part-ML (ML.A.801) and Part-CAO (CAO.A.065 and CAO.A.070) contain their own CRS rules. This article focuses on Part-145. For the full approval, see our EASA Part-145 guide.
Who can sign a CRS
Under EASA, a CRS is signed by a person, but on behalf of the organisation. That person needs two things: a Part-66 licence with the right category and ratings, where Part-66 applies, and a certification authorisation issued by the organisation under 145.A.35. The authorisation defines what each person may certify.
Point 66.A.20 of Part-66 sets the privileges of each licence category:
| Category | What the holder may certify | Typical use |
|---|---|---|
| A | Minor scheduled line maintenance and simple defect rectification, limited to tasks endorsed on the authorisation and work the holder personally performed | Line maintenance, task-trained mechanics |
| B1 | Maintenance on structure, powerplant and mechanical and electrical systems, plus avionic work that needs only simple tests | Line and base maintenance, and B1 support staff in base |
| B2 | Maintenance on avionic and electrical systems, and electrical and avionic tasks within powerplant and mechanical systems that need only simple tests | Avionics work, and B2 support staff in base |
| C | Base maintenance of the aircraft, with privileges for the aircraft in its entirety | Release of a base maintenance check |
Part-66 also has B2L, B3 and L categories for smaller aircraft. In base maintenance of complex motor-powered aircraft, 145.A.30(h) requires category C certifying staff supported by B1 and B2 staff. The B1 and B2 support staff ensure that all relevant tasks or inspections meet the required standard. Then the category C certifying staff checks that all customer work was done and assesses the impact of any work not carried out. In line maintenance, 145.A.30(g) requires aircraft-rated certifying staff under 145.A.35.
Under the FAA, a certificated repair station must inspect each article before approving it for return to service (14 CFR 145.213). For a domestic repair station, each person authorised to approve an article for return to service must be certificated as a mechanic or repairman under part 65 (14 CFR 145.157). Foreign repair stations follow the training and experience criteria in 145.157(b).
What a CRS must contain
AMC 145.A.50(b) gives the standard statement:
"Certifies that the work specified, except as otherwise specified, was carried out in accordance with Part-145 and in respect to that work the aircraft/aircraft component is considered ready for release to service."
The same AMC adds these points:
- The CRS should reference the EASA Part-145 approval number and the identity of the person who issued it.
- An abbreviated statement, "Part-145 release to service", is acceptable if the technical log shows the full statement in its introduction.
- The CRS should relate to the task in the instructions of the (S)TC holder, the operator or the aircraft maintenance programme.
- The date should show when the maintenance took place relative to life or overhaul limits: date, flight hours, cycles or landings, as appropriate.
- After extensive maintenance, the CRS may summarise the work if there is a unique cross-reference to the work package that contains the full details.
Point M.A.801(e) of Part-M gives the minimum content in a similar way: basic details of the maintenance, the completion date, the identity of the organisation or person issuing it, and any limitations to airworthiness or operations.
Aircraft CRS vs component release: EASA Form 1 and FAA Form 8130-3
A component maintained off the aircraft also needs a release. Under 145.A.50(d), the EASA Form 1 is the component certificate of release to service, with some exceptions in Part-M and Part-ML. AMC2 145.A.50(d) adds that the component then needs a second CRS when it is installed on the aircraft. Form 1 releases the component. It does not release the installation.
| Situation | EASA | FAA |
|---|---|---|
| Aircraft after maintenance | CRS under 145.A.50, usually in the technical log or work package | Maintenance record entry with signature, certificate number and kind of certificate (14 CFR 43.9) |
| Aircraft after a required inspection | CRS, plus Part-M or Part-CAMO records | Inspection entry under 14 CFR 43.11, with a signed discrepancy list if not approved |
| Component maintained off the aircraft | EASA Form 1, block 14a "Part-145.A.50 Release to Service" | FAA Form 8130-3, blocks 14a to 14e, or a maintenance record entry |
| Installation of the component | A separate aircraft CRS | A separate maintenance record entry; the 8130-3 is not approval to install |
On the FAA side, 43.9(a)(4) says that the signature "constitutes the approval for return to service only for the work performed". 14 CFR 43.5 adds that no one may approve a return to service unless the 43.9 or 43.11 entry has been made. Since September 2025, the guidance on using FAA Form 8130-3 for return to service after maintenance is in AC 43-9D (dated 9/22/25), which cancelled AC 43-9C. Order 8130.21J now covers the form under Part 21 only. AC 43-9D also states that the 8130-3 is not used for aircraft return to service and is not a shipping document.
Records and electronic signatures
A CRS is only as strong as the records behind it. Under 145.A.55(a), the organisation must keep all records needed to prove that the requirements for the CRS were met, including subcontractor release documents. It must give the customer a copy of each CRS with the associated detailed records, and keep its copies for 3 years from the release. AMC1 145.A.55(a)(3) adds that records should refer to the revision status of the maintenance data used. Under the FAA, a repair station keeps its records in English for at least 2 years from the return to service, and gives the owner or operator a copy of the maintenance release (14 CFR 145.219).
Electronic records are accepted by both authorities, with conditions:
- EASA, records: AMC1 145.A.55 accepts paper, electronic or mixed records. Computer systems should have at least one backup updated within 24 hours of any new entry, stored in a different location, and safeguards against unauthorised changes.
- EASA, Form 1: the AMC to Appendix II to Part-M accepts an electronic EASA Form 1. The electronic signature must be uniquely linked to the signatory, identify the signatory and be under the signatory's sole control. The system must not allow signing a blank form, and the procedure is submitted to the competent authority with the exposition. Block 14b then reads "Electronic Signature on File".
- FAA: AC 120-78B, issued in December 2024, replaced AC 120-78A as the guidance for electronic signatures, electronic recordkeeping and electronic manuals. AC 43-9D also warns that many computerised maintenance tracking systems do not, by themselves, meet the record requirements of 43.9 or 91.417, including signatures.
In both frameworks, the use of electronic signatures must be described in your procedures (the MOE under EASA, the repair station manual under the FAA) and accepted by your authority.
Common CRS errors
Most CRS findings come from the work package behind the signature:
- Incomplete work package. A task card is unsigned, an inspection stamp is missing or a step has no recorded value.
- Missing references. The task card does not cite the maintenance data or its revision, or the CRS has no unique cross-reference to the work package.
- Open items not declared. Defects or tasks not completed, without agreement from the CAMO or operator and without the statement required by 145.A.50(e).
- Wrong signatory. The person's authorisation does not cover that aircraft type, category or task, or it has expired.
- Component documentation gaps. Parts installed without a valid EASA Form 1 or FAA 8130-3 on file.
- Overdue ADs. GM1 145.A.50(a) treats an overdue AD as a hazard to flight safety, which blocks the CRS.
Pre-CRS checklist
Before certifying staff sign, the package should pass these checks:
- All ordered tasks are signed, including independent inspections where required.
- Each task card references the maintenance data and its revision.
- Non-routine cards are closed, or deferred with written agreement from the party responsible for continuing airworthiness.
- Any incomplete maintenance and its limitations are written into the CRS.
- Every installed part has its release certificate and matching part and serial numbers.
- Tools used are recorded and were within calibration; no tools are missing at close-out.
- The certifying staff member holds a valid authorisation for the type, category and task.
- The CRS shows the approval number, the signatory, the date and hours or cycles, and the work package reference.
How software supports a clean CRS
Software does not issue the CRS. The authorised certifying staff member does, and the organisation remains responsible under its approval. What software can do is make the package complete and the evidence easy to find, as we describe in how to manage work orders and task cards.
In SkyPlannerHub, line and base maintenance run on work orders and scheduled tasks, with compliance tracking by aircraft and fleet. Technicians open task cards on a tablet or phone and sign with their own user. When the work is certified, the system checks that the person holds the licence and type rating for that aircraft. Certification management tracks licences, ratings and authorisations with expiry alerts.
The same platform keeps the evidence that a CRS depends on: aircraft and component history with hours, cycles and airworthiness status, AD, SB and life-limited part tracking with alerts before each limit, inventory traceable by serial number, batch and certificate, and role-based access with full action auditing. Your MOE procedures and your authority's acceptance still decide how you use electronic records.
Frequently asked questions
Does a CRS mean the aircraft is airworthy?
Not necessarily. According to GM1 145.A.50(a), a CRS certifies the maintenance that was ordered. Airworthiness before each flight remains the responsibility of the person or organisation managing the aircraft's continuing airworthiness.
Can a CRS be issued if some work is not completed?
Yes, within limits. Under 145.A.50(e), the organisation may issue a CRS within the approved aircraft limitations and must state the incomplete work in the CRS. It cannot issue one with a known non-compliance that endangers flight safety.
Is an EASA Form 1 the same as an FAA 8130-3?
They play the same role: a release certificate for a component. Each is issued under its own authority's rules. Whether one is accepted by the other authority depends on the bilateral agreements in force. Neither form approves the installation on an aircraft.
Can a CRS be signed electronically?
Yes, if your procedures describe it and your authority accepts it. EASA guidance sets criteria for electronic signatures and records, and the FAA guidance is AC 120-78B. The signature must identify the person and be under their sole control.
Conclusion
A CRS is a short statement with a lot behind it: complete task cards, current data, closed or agreed open items, traceable parts and an authorised signatory. Get the package right and the signature is the easy part. If you want to see how SkyPlannerHub prepares that package with your own processes, talk to our team.