F-35 fighter-bomber will be the first fighter, in a long time, to lack a HUD (head-up display). The HUD will still be present, but as part of the Helmet Mounted Display System (HMDS). The U.S. Air Force recently decided to equip all F-35s, including exported models, with the HMDS. The production models of the HMDS are in production now, but at a very low rate (fewer than twenty a year). The F-35 HMDS helmets cost nearly a million dollars each, and mass production will begin in about three years. One reason for this is continued efforts to reduce the weight of the HMDS. The day version weighs about four pounds, and the night version (with night vision capabilities), about five pounds. This is about a pound more (for each version) than current non-HMDS helmets.
With an HMDS, the HUD information will be displayed on the inside of the pilots visor, while still enabling the pilot to see through the visor. This type of helmet visor has been around for over a decade, but concentrated on allowing the pilot to control weapons by just looking at targets, and pressing the "fire" button at the right time. Now, the display technology inside the helmet has reached the point where it can handle the HUD stuff as well. The weight of these HMDS systems has come down as well, making it easier to wear them for long periods of time.
The HUD was a big innovation for fighters, as it made it possible for the pilot to spend more time with his head up, keeping an eye on the sky, or an ongoing battle. The military HUD has been around for half a century, but appears set to disappear as more pilots shift to HMDS.
Over the last few years, the visor displays have added the display of critical flight and navigation information. This, in addition to the basic function of enabling the pilot to turn his head, get an enemy aircraft into the crosshairs displayed on the visor, and fire a missile that will promptly go after target the pilot was looking at.
These helmet displays allow the pilot look around more often without having to look down at cockpit displays, or straight ahead at a HUD (Head Up Display.) This kind of freedom gives an experienced pilot an extra edge in finding enemy aircraft or targets, and maneuvering to get into a better position for attacks. It's also useful for air to ground attacks.