The F-35, the U.S. Armed Forces’ most expensive project to date, may be outdated before it’s even been deployed, The Washington Free Beacon reports, citing U.S. officials and defense analysts.

This time, it’s not the plane’s lack of structural integrity or even questions of relevance in combat.

Instead, the F-35 could face irrelevance because the Chinese reportedly stole secrets about the fighter jet and incorporated them into the latest Chinese stealth fighter.

“If as part of their espionage, China had also gained engineering insights into the F-35′s very advanced sensor systems, that could prove disastrous to its combat potential barring a rapid redesign and improvements before entering service,” Richard Fisher, a Chinese weapon systems specialist, told The Washington Free Beacon.

Bill Gertz, writing for The Washington Free Beacon, reports:

The F-35 data theft was confirmed after recent photographs were published on Chinese websites showing a newer version of the J-20. The new version of the radar-evading aircraft had incorporated several design upgrades since the first demonstrator aircraft was revealed in 2011.

The design upgrades to the J-2o include an electro-optical targeting system under its nose, which gives it better surveillance and strike capabilities and appears to be inspired by the F-35.

Until now, this placement and technology was thought to have given the F-35 unrivaled situational awareness, a necessary insurance for the F-35 having slightly limited in-flight maneuverability. This leak could call into question the F-35’s practicality in military situations.

We reached out to Lockheed Martin, the maker of the F-35, for comment and will update this post if we hear back.