FARNBOROUGH England (Reuters) - U.S. military officials have approved a limited flight clearance for the Lockheed Martin Corp (>> Lockheed Martin Corporation) F-35 fighter jets that mandates engine inspections and certain flight restrictions, while an investigation continues into a massive engine failure that grounded the entire fleet, the Pentagon said on Tuesday.

Pentagon spokesman Rear Admiral John Kirby said U.S. officials remained hopeful that the F-35 could make its international debut at the Farnborough air show, but no decision had been made.

"This information is an encouraging step, but no final decision has been made at this time," Kirby said in a statement. "Safety remains the overriding priority."

(Reporting by Andrea Shalal; Editing by Mark Potter)