Ackermand et al.(2006): Lazulite-bearing metaquartzite of the Itremo Group (Central Madagascar); Scientific significance and economic importance in Proceedings of the Malagasy-German Research Cooperation in Life and Earth sciences, 5-18
The fastest fighter aircraft is the MiG 25, with speeds topping at Mach 3.2 (2,450 mph/4,000 km/h). Pilots were not allowed to go beyond Mach 2.8. Above Mach 2.8, the engines would overheat and burn up.
The so-called X-plane would travel at Mach 20 â roughly 13,000 mph (20,900 kph) â allowing the military to reach any spot on the globe in less than an hour.