The search for five U.S. Army aviators who went missing off the Hawaiian island of Oahu on Aug. 15 during a night-time training operation has been called off.

“A decision to suspend searching without finding survivors is extremely difficult given the depth of its impact and I know I speak for the entire Coast Guard when I say our thoughts and prayers are with Army helicopter squadron and particularly with families and loved ones of those missing,” Rear Adm. Vincent B. Atkins, a Coast Guard commander, wrote in a statement released Monday.