Getting the TU-144 built before the Concorde (and therefore proving Soviet superiority to the world) was allegedly a high priority for the Soviets. The plane was developed under a tight schedule and relied on a few less advanced aviation technologies. The TU-144 suffered three known crashes, the most famous being at the 1973 Paris Air Show (there are conflicting theories on the cause of the 1973 crash). In regular passenger service, the TU-144 proved unreliable. Only one flight a week was permitted on a single route between Moscow and Almaty, Kazakhstan. It is rumoured that Soviet leaders were nervous about the 144's airworthiness and ordered it's chief designer Alexei Tupolev to personally inspect every 144.