Russia has developed an OBOG (OnBoard Oxygen Generating) system for its latest combat aircraft, the T-50. Russia still uses oxygen bottle systems (weighing about 90 kg/198 pounds) for its aircraft. This means that pilots operating at altitudes higher than 4,000 meters (12,000 feet) have to monitor their air as well as their fuel supplies. The new Russian OBOG design weighs only 30 kg (66 pounds), is more compact, and supplies far more oxygen that the equivalent weight of bottled oxygen. Russia plans to begin replacing oxygen bottles with the new OBOGs in all its aircraft. India also recently developed an OBOG that will first be installed in the new LCA (Light Combat Aircraft) as a technology demonstrator. Eventually, this OBOG will be installed in all Indian high-altitude warplanes.
Although OBOGs have been around for over half a century, only in the last two decades have OBOGs become compact, cheap, and reliable enough to replace the older compressed gases or LOX (liquid oxygen) as a source of breathable air for high flying aircrew. Aircraft have been staying in the air longer (because of in-flight refueling) and carrying enough compressed oxygen has become untenable, so it has become necessary for OBOG to replace it. Since the 1990s, most American military aircraft have replaced older oxygen systems with OBOG. Most Western nations, and now Russia, have followed, at least with their latest model aircraft.
Most OBOG systems work by using a chemical reaction to remove nitrogen from the air taken in to the OBOG, and then sending out air with the proper amount of oxygen to the aircrew.