F-35 stealth fighter is still struggling with a string of big problems even as the Pentagon talks about ramping up production

• The F-35 Lightning II Joint Strike Fighter continues to face a number of serious deficiencies that could negatively impact pilots and missions, Defense News reports.
• The fifth-generation stealth fighter struggles with things like cabin pressure spikes that cause ear and sinus pains and loss of aircraft control with certain maneuvers.
• Defense officials have downplayed the seriousness of these issues as the Pentagon and Lockheed discuss ramping up to full-rate production.
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America's most expensive weapon - Lockheed Martin's F-35 Lightning II Joint Strike Fighter - is still struggling with a number of serious problems, such as destructive chain reactions triggered by a flat tire, a weird green glow on the helmet display that makes it difficult to land on aircraft carriers, and a loss of stealth at supersonic speeds.

Documents obtained by Defense News indicate that the US military's fifth-generation F-35 stealth fighters continue to suffer from more than a dozen issues that could potentially put pilots at risk or jeopardize a mission.

The F-35 program managed to cut the number of category 1 deficiencies down from 111 at the start of last year to 64 in May 2018 to just 13 as the aircraft headed into operational testing last fall. But some of the remaining issues are very problematic.

For instance, in cold weather conditions, the F-35 may falsely report that a battery has failed, a problem that has resulted in aborted missions.

When its hot out, older engines on the short takeoff/vertical landing variant sometimes have trouble producing the necessary thrust to keep the fighter in the air, leading to an unplanned a hard landing.

There have also been issues with unusual spikes in cabin pressure in the cockpit causing pain in the ears and sinuses, Defense News reports.

One particular problem that really stood out to a retired fighter pilot was that in some cases, after completing certain maneuvers, F-35B and F-35C pilots have lost the ability to fully control the fighter's pitch, roll, and yaw.

The F-35 program, by the US military's own admission, has been "troubled," suffering from production problems, ballooning costs, delivery delays, and numerous technical challenges.

Acting Secretary of Defense Patrick Shanahan has colorfully described the F-35 program, the cost of which recently grew by tens of billions of dollars, as "f---ed up."

Read more: Here are 5 of the worst weapons projects the US military has in the works

News of the F-35s problems comes as the Pentagon and Lockheed discuss ramping up to full-rate production, increasing annual delivery from 91 to 160 jets within the next few years. The F-35 Joint Program Office told Defense News that not all of the problems will be addressed before the full-rate production decision.

While the problems reported by Defense News sound alarming, defense officials who spoke to the outlet downplayed their seriousness, with one explaining that the current category 1 deficiencies affecting the F-35 are ones "that have a mission impact with a current workaround that's acceptable to the war fighter with the knowledge that we will be able to correct that deficiency at some future time."

A naval aviator told the outlet that the current problems are "growing pains" that are to be expected.