A Saudi Arabian trainee pilot and his Filipino instructor have been missing for a week after their plane disappeared during a training session in the Philippines.

On May 18, Abdullah Khalid Al Sherif, 23, who had been attending an aviation school in the Philippines, had a training flight around Occidental Mindoro province, Gulf News reported. Contact with the plane was lost and it disappeared from radar.

Sherif’s family speculated that the plane might have been hijacked. His brother, Adbul Majid, is now in the Philippines to help in the search.

“Evidence and information available to us indicate that the aircraft has been hijacked,” Majid said.

The Saudi Embassy in Manila said it was working with Philippine authorities to locate the two men. The report did not identify the Filipino instructor.

“We will continue to make efforts to search for him in coordination with the Philippine Interior Ministry, the Defense Ministry, the Civil Aviation Authority and other agencies concerned,” the embassy said.