The incident, which occurred east of Okinawa on November 30, was reported by Japanese media at the time, but it wasn't until December 4 that US Air Force officials confirmed the report.
The loss of one of the plane's panels, measuring approximately 12 inches (30 centimeters) by 24 inches (60 centimeters), was noticed by the F-35's wingman as the aircraft was in the process of landing.
Specialists suggested that the panel was broken during the flight, given the fact that the F-35 was thoroughly inspected ahead of the takeoff.
It is still unclear whether the replacement of the lost part of the plane's fuselage will be possible without compromising its flight safety.
The F-35 Lightning II is the second US fifth-generation fighter after the F-22 Raptor.
Interesting thoughts on why that f-35 panel may have ripped off.— Valerie Insinna (@ValerieInsinna) 5 декабря 2017 г.
(Thanks to all who share info like this btw; you make me smarter.) https://t.co/VlzgBlcLHf
The program to create the F-35 is estimated to have cost about one and a half trillion dollars, something that turns this fighter jet into the world's most expensive aircraft.
The project has repeatedly been slammed, including by US President Donald Trump, over a whole array of technical problems.
In October, representatives of the US Air Force were cited as saying that many F-35 pilots had symptoms of oxygen deficit.
In November, US government officials said that the US Defense Department refused to accept the delivery of F-35s between September 21 and October 20 after finding "corrosion exceeding technical limits" around fasteners holding the planes' exterior coatings to their airframes.