Warning over safety as jets return Airlines urged to take extra care published : 16 Dec 2020 at 12:00 27 Delta Air Lines passenger planes are seen parked due to flight reductions at Birmingham-Shuttlesworth International Airport in Birmingham, Alabama on March 25. (Reuters photo) SYDNEY: Regulators, insurers and experts are warning airlines to take extra care when reactivating planes left in extended storage during the Covid-19 pandemic, citing potential pilot rustiness, maintenance errors and even insect nests blocking key sensors. The unprecedented number of aircraft grounded as coronavirus lockdowns blocked air travel -- at one point reaching two-thirds of the global fleet -- has created a spike in the number of reported problems as airlines return them to service.