The fighter jet returned to Kadena Air Base at 10:24 a.m. local time on Monday missing a 12 inch by 18 inch hexagonal side panel that weighed two pounds (0.9 kilograms), spokesperson Robert Dabbs confirmed in an email.
Dabbs said the panel fell from below the aircraft's cockpit on the right side. There have been no reports of any further damages or injuries as a result of the incident, and an investigation into the incident remains ongoing.
The panel covered electronic devices and without it the aircraft could lose its stealth capabilities, reports have indicated.
The F-35 incident is not the first to grab headlines in the region, with past aircraft mishaps having prompted locals to call on the US military to implement preventative measures. In late 2017, the window of a Super Stallion chopper broke off and crashed into a field used by a local elementary school, where dozens of children had been playing at the time.
The latest comes after the US military grounded its entire fleet of V-22 Ospreys after a training mission off the Japanese coast turned fatal when the tiltrotor aircraft crashed, killing all aboard. The grounding came in response to preliminary findings that indicated the incident was the result of a non-human error. Similar to the F-35, the Osprey has been involved in several accidents.