Coast Guard searching for plane believed to have crashed into Gulf of Mexico

— -- Radar contact was lost Wednesday night with a general aviation aircraft believed to have crashed into the Gulf of Mexico with an unresponsive pilot aboard, according to officials.

North American Aerospace Defense (NORAD) Command had earlier launched fighter aircraft based in Texas and Louisiana to make visual contact with the single-engine plane that had failed to land in Texas after having taken off from Oklahoma City earlier in the day.

"A Cirrus S22T left Wiley Post Airport in Oklahoma City this afternoon and the pilot filed a flight plan to Georgetown, Texas," the Federal Aviation Administration said in a statement. "The pilot did not land in Georgetown, continued on the same course and was unresponsive to air traffic control instructions. The aircraft was last observed on radar about 219 miles northwest of Cancun at 15,000 feet and was headed into the Gulf of Mexico."

The U.S. Coast Guard and Mexican authorities were brought into the search for the plane that is believed to have crashed into the Gulf of Mexico. The Coast Guard said on Thursday that the pilot's condition was "likely due to hypoxia" -- a condition that occurs when the body is deprived of oxygen.

The pilot was identified as Dr. Bill Kinsinger, 55, of Oklahoma City, Oklahoma, in a Coast Guard press release Thursday afternoon.

"No signs of the plane have been located, and Coast Guard aircrews are scheduled to continue searching through the night," the release said.

The FAA first made radar contact with the missing aircraft at 3:36 p.m. CT. Shortly afterward, NORAD launched two F-16 fighters from Ellington Field Joint Reserve Base in Houston to attempt to make visual contact with the plane.

"They tried to make radio communications contact with the pilot, as well as doing some basic military maneuvers around the aircraft to get the pilot’s attention but the pilot was unresponsive," said Maj. Mary Ricks, a spokeswoman for NORAD and U.S. Northern Command.

The F-16 pilots determined that only the pilot was aboard the aircraft.

Two additional F-15s from New Orleans, Louisiana, were launched to replace the F-16s that were running low on fuel as they continued to follow the plane over the Gulf of Mexico.

However, Ricks said the F-15s were not able to reach the plane to make visual contact.

Once the aircraft was over the Gulf of Mexico, NORAD contacted the Coast Guard, which dispatched three aircraft to assist in the search. NORAD and the FAA also coordinated with the State Department to notify the Mexican government about the plane's status.

Mexican authorities tracked the aircraft on radar but then lost visibility with it at 6:08 p.m. CT.

At that point, the F-15s returned to the base since they had not made visual contact with the plane.