The F-35A jets from Hill Air Force Base in Utah landed at RAF Lakenheath on Saturday for what the Air Force said was several weeks of training with other US aircraft and crews and those from North Atlantic Treaty Organization allies.

“As we and our joint F-35 partners bring this aircraft into our inventories, it’s important that we train together to integrate into a seamless team capable of defending the sovereignty of allied nations,” Gen. Tod D. Wolters, commander of US Air Forces in Europe, said in a statement.

The Air Force said the F-35s were deploying to support the European Reassurance Initiative, a multibillion dollar program started under President Obama in 2014 to show support for US allies after Russia annexed the Crimea from Ukraine.