NATO and U.S. flags flutter as U.S. Air Force F-22 Raptor fighter flies over the military air base in Siauliai, Lithuania, April 27, 2016. (Photo by Ints Kalnins/Reuters)

A service member of the Ukrainian armed forces is seen at fighting positions on the line of separation from pro-Russian rebels in Donetsk region, Ukraine on April 10, 2021. (Photo by Oleksandr Klymenko/Reuters)

A pale tussock moth (Calliteara pudibunda) larva or caterpillar just after moulting on heather on Hankley Common, Surrey, England on April 30, 2019. (Photo by Gillian Pullinger/Alamy Stock Photo)

Sunrise in Ely, Cambridgeshire on April 15, 2020 by the River Great Ouse, England. The warm weather is set to continue until the weekend. (Photo by Veronica Johansson Poultney/Bav Media)

A municipality worker in a protective suit feeds street cats at Sultanahmet Square, as the spread of coronavirus disease (COVID-19) continues in Istanbul, Turkey, April 9, 2020. (Photo by Umit Bektas/Reuters)

Russian Orthodox priest, Father Nikolai Gensitsky, speaks with believers while having a festive meal during the Easter celebrations in a church in the village of Yekaterininskoye in Omsk Region, Russia on April 19, 2020. (Photo by Alexey Malgavko/Reuters)

A participant takes part in a zombie parade during the Brussels International Fantastic Film Festival in Brussels, Belgium, April 9, 2016. (Photo by Yves Herman/Reuters)

Singer Halsey has her dress adjusted before she poses during the premiere of the film “The Huntsman: Winter's War” in Los Angeles, California, April 11, 2016. (Photo by Kevork Djansezian/Reuters)