The first F-35A frame constructed in Japan, pictured, crashed into the Pacific Ocean April 9. File Photo courtesy of Japan's Ministry of Defense

April 17 (UPI) -- In the months before Japan's first F-35A stealth fighter jets crashed in the Pacific Ocean, the country's air force made seven emergency landings of the aircraft, Defense Minister Takeshi Iwaya said.

The Japanese air force began using its fleet of 13 F-35As in January, and on April 9, the first plane off Mitsubishi's assembly line crashed off northern Japan.


Speaking during a news conference Tuesday, Iwaya said the seven precautionary landings each happened before the end of February. Of those landings, seven involved aircraft assembled in Japan and one assembled in the United States. The plane that crashed made two of the emergency landings.

Iwaya said a pilot made one landing in response to a cooling system warning light and another pilot made a landing due to a navigation system problem.

"The technology on board the F-35 is highly classified," Iwaya said. "With cooperation from the U.S., we would like to take the initiative in thoroughly investigating the causes while gaining cooperation from the United States."

Though the Japanese coast guard and U.S. Forces Japan suspended their search for the missing pilot from the April 9 crash, the Japan Maritime Self-Defense Force search was underway.

"Though U.S. search and rescue efforts have ended, we will continue to coordinate with our Japanese partners on efforts to locate and recovery the missing aircraft," U.S. Air Force Col. John Hutcheson told Stars and Stripes.

Japan grounded its fleet of 13 F-35As in the wake of the crash.