Returning aircraft to service that have been parked or stored during the COVID-19 pandemic - Civil Aviation Safety Alert (CASA) No. 2021-01


Aircraft owners, operators, approved maintenance organizations and aircraft maintenance engineers

File Classification No.: Z 5000-35
RDIMS No.: 17118119
Document No.: CASA 2021-01
Issue No.: 01
Effective Date: 2021-02-08


The purpose of this CASA is to provide guidance to aircraft owners, operators, Approved Maintenance Organizations (AMOs) and holders of Aircraft Maintenance Engineer (AME) licences, as they plan to return to service aircraft that have been parked or stored for long periods.


Due to the COVID-19 crisis, many aircraft owners decided to either park or put their aircraft into storage.

Depending on the circumstances under which aircraft were parked or put into storage, and the length of time in storage, additional inspections or maintenance may need to be performed to ensure that aircraft are returned to service in an airworthy condition.

Scheduled maintenance may be due or overdue and additional maintenance may be required. The scope of additional maintenance required will vary depending on factors such as aircraft type, condition of the aircraft, age, how and where the aircraft was parked or stored, period of inactivity and recommendations from the aircraft manufacturer or applicable design approval holder.

Some hazards caused by long periods of storage may not be evident. Aircraft condition may be affected by exposure to the elements, bird or insect infiltration, pitot or static blockage, etc.

Aircraft owners and operators are reminded that aircraft can only be operated if they are:

  • (a) airworthy - in conformity to the type design and safe for flight;
  • (b) appropriately equipped and configured for their intended use; and
  • (c) maintained in accordance with their approved maintenance schedule.

Recommended action:

In order to ensure an aircraft is airworthy after being parked or stored it may be necessary to perform maintenance tasks that are not specifically required by the Operator or the applicable aircraft maintenance schedule, but are prudent in light of experience, or recommendations made by the aircraft manufacturer or design approval holder. These maintenance tasks may include:

  • 1) calendar items of an approved aircraft maintenance schedule which includes applicable Standard 625 Appendix C out of phase tasks;
  • 2) aircraft, engine and propeller design approval holder recommendations for storage;
  • 3) humidity control of engines and interior of aircraft;
  • 4) fuel contamination checks (water infiltration);
  • 5) tire flat spotting;
  • 6) wheel bearing corrosion checks;
  • 7) etc.

The need to perform additional maintenance tasks may affect a planned return to service date.

Since parked or stored aircraft have not been operated, maintenance tasks that are based on flight cycles or flight hours may or may not need to be accomplished prior to the aircraft being returned to service.

Maintenance schedule tasks expressed in calendar time that have come due during the period of aircraft storage must be accomplished prior to the next flight, as the concept that calendar time stops when an aircraft is taken out of service is not supported by the Canadian Aviation Regulations (CARs).

Aircraft, engine and propeller instructions for continued airworthiness (ICAs) typically include instructions for storage. If the ICAs do not contain storage instructions, the manufacturer or design approval holder should be consulted.

If the manufacturer or design approval holder instructions were not followed, or the storage period extended beyond the length covered in the storage instructions, then the aircraft will not have been maintained in accordance with the applicable standards of airworthiness. In such a case, a plan for ensuring that the applicable maintenance tasks are performed in order to ensure the aircraft is airworthy should be developed in consultation with the applicable manufacturer or design approval holder.

Other manufacturer or design approval holder recommendations such as operator notifications (e.g. service letters or notices) may address the topic of return to service following storage.

Before returning the aircraft to service, owners and operators may wish to consider performing a flight (non-revenue) to check proper functioning of the aircraft and all the aircraft systems.

Other information:

The European Union Aviation Safety Agency (EASA) has written documents addressing the return to service of aircraft from storage. They are:

  • - Return to service of aircraft from storage guidelines in relation to the COVID-19 pandemic.
  • - SIB 2020-14: Pitot-Static Issues After Storage due to the Covid-19 Pandemic.

As of the publication date of this CASA, the EASA documents are available at the link:

Transport Canada Civil Aviation suggests that aircraft owners, operators, AMOs, and AMEs also consider the advice in the EASA documents, taking into consideration the differences between the regulatory frameworks under the CARs, and adapt it to their own circumstance as necessary.

Contact office:

For more information concerning this issue, contact a Transport Canada Centre; or contact Jeffrey Phipps, Operational Airworthiness, Standards Branch in Ottawa, by telephone at 343-999-8145 or by e-mail at

Original signed by

Félix Meunier
Standards Branch

The Transport Canada Civil Aviation Safety Alert (CASA) is used to convey important safety information and contains recommended action items. The CASA strives to assist the aviation industry's efforts to provide a service with the highest possible degree of safety. The information contained herein is often critical and must be conveyed to the appropriate office in a timely manner. The CASA may be changed or amended should new information become available.