From pickling to bird nests and insect invasions, the threats posed to incorrectly stored aircraft are legion. Paul Willis reports on return-to-service requirements.

As the global travel industry emerges slowly from the impact of the COVID-19 crisis, a growing number of airplanes are returning to service.
As an example, at the height of the pandemic Lufthansa had about 75% of its fleet parked, half of which were being held in long-term storage. In the year and a half since, the carrier has gradually been taking its aeroplanes out of storage as governments around the world were lifting restrictions on travel and the COVID-19 vaccine was becoming more widely available. At the time of writing, Lufthansa had about a third of its fleet parked, with 530 active aircraft – compared with about 800 before the crisis.