Cockpit pressure causing pilots sinus pain and a coating that “blisters” at supersonic speeds are among an array of new problems detected in a multi-billion US warplane.

Nine major faults were identified in the F-35 stealth fighter jet as it entered service last year, according to US journal Defence News.

Australia has ordered 72 of the warplanes, built by US aerospace giant Lockheed Martin, at a cost of $125 million each.

The F-35 is arguably the most advanced fighter jet in the skies. But the warplane has been plagued by problems. (Cover Images)

The F-35 has been touted as the world’s most lethal jet fighter - it is almost undetectable by radar and flies at one-and-a-half times the speed of sound.

But the warplane’s development is way behind schedule and billions of dollars over budget.

And the new unreported faults suggest the aircraft may be in worse shape than the public realised. As well as putting pilots at risk they threaten the plane’s combat effectiveness.

Faults include a 'green glow' that can obscure the pilot's helmet mounted display, making it difficult to land the aircraft. (AP)

The problems include spikes in cockpit pressure that cause pilots “excruciating” ear and sinus pain. At supersonic speeds the aircraft’s stealth coating – designed to make it invisible to radar – would “blister”.

Sometimes a “green glow” appeared on the pilot’s helmet-mounted display, obstructing helmet images, making it difficult to land the plane.

The faults also included a loss of control during certain manoeuvres, and in very cold temperatures, false alarms of battery failure.

Lokheed-Martin, manufacturers of the F-35 fighter, is confident they can fix the faults. (AP)

Lockheed-Martin vice-president Greg Ulmer said the company was working to fix the problems.

“These issues are important to address, and each is well understood, resolved, or on a path to resolution,” he said.

Senior US military officers have admitted that the aircraft program has been “troubled”. Acting Defence Secretary Patrick Shanahan, a former Boeing executive, has described it as “f----d up”.