Deep in the Sahara, the C.I.A. is continuing to conduct secret drone flights from a small but steadily expanding air base, even as the Biden administration has temporarily limited drone strikes against suspected terrorists outside conventional war zones, such as Afghanistan. Soon after it set up the base in northern Niger three years ago, the C.I.A. was poised to launch drone strikes from the site. But there is no public evidence that the agency has carried out anything but surveillance missions so far. New satellite imagery shows that the air base in Dirkou, Niger, has grown significantly since The New York Times first reported the C.I.A. operations there in 2018, to include a much longer runway and increased security. The new imagery also shows for the first time what appears to be an MQ-9 Reaper drone taxiing to or from a clamshell hangar. Under a directive that Mr. Biden's national security adviser, Jake Sullivan, quietly imposed on Jan. 20, Inauguration Day, the military and the C.I.A. must now obtain White House permission to attack terrorism suspects in poorly governed places where there are scant or no American ground troops, such as Somalia, Yemen and Libya. Under the Trump administration, they had been allowed to decide for themselves whether circumstances on the ground met certain conditions and an attack was justified. A recent report by the International Crisis Group concluded that the military-first strategy of France and its allies, including the United States, has failed.