Contrails, one of the most visible anthropogenic atmospheric phenomena, are line-shaped clouds produced by the aircraft engine. The climatic impact of contrails (for example, the warming effect to the surface temperature) has been a long-standing issue of debate, mainly because the ever-increasing aviation activities are intertwined with the global warming background, making the factorial analysis impossible to carry out from the observational perspective. The COVID-19 pandemic has hit the aviation industry with a 55% decline in the number of flights globally, which provides us a valuable opportunity to quantify the change in contrails and their subsequent impacts on the global climate.