The Coast Guard has suspended its search for the Hurlburt Field airman who from from an C-130 Hercules transport aircraft during a training exercise over the Gulf of Mexico.

Coast Guard air and boat crews spent more than 130 hours searching nearly 5,000 square nautical miles in search of the airman, who was assigned to the 24th Special Operations Wing, the service announced on Friday.

Air Force recovery teams “are currently refining and adjusting the search area as efforts continue,' according to an Air Force statement

“We would like to extend our gratitude to all of the federal, state and local units that have aided in the search for our Airman, especially the U.S. Coast Guard,” 24th Special Operations Wing commander Col. Matt Allen said in a statement. “We will continue our recovery effort as long as circumstances and resources allow to bring our Airman home.”

The airman was lost when he “exited his aircraft during a jump training scenario over the Gulf of Mexico approximately 4 miles south” of Hurlburt Field in Florida, according to an earlier Air Force statement.

Crew members aboard the C-130 “initially saw the airman treading water but lost sight of him while making a turn in an effort to pick him up,” Fox News reports.

The Air Force is investigating the incident and will not release the name of the airman involved pending a next-of-kin notification.