India has developed an OBOG (OnBoard Oxygen Generating) system for its combat aircraft. Although such systems 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.
Because aircraft have been staying in the air longer (because of in-flight refueling), carrying enough compressed oxygen becomes untenable, and OBOG replaces it. Since the 1990s, most American military aircraft have replaced older oxygen systems with OBOG. Most Western nations, and 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. The new Indian OBOG will first be installed in the new LCA (Light Combat Aircraft) as a technology demonstrator. Eventually, the OBOG will be installed in all Indian high-altitude warplanes.