NASA has postponed the launch of its flagship James Webb Space Telescope to early 2021 owing to a range of factors influencing its schedule and performance, including the technical challenges and tasks remaining before launch. The telescope's new total lifecycle cost, to support the revised launch date, is estimated at $9.66 billion; its new development cost estimate is $8.8 billion, the US space agency said in a statement. An Independent Review Board (IRB) established by NASA to assess progress on the world's premier science observatory unanimously recommended that its development should continue. "Webb should continue based on its extraordinary scientific potential and critical role in maintaining US leadership in astronomy and astrophysics," said Tom Young, the chair of the review board. "Ensuring every element of Webb functions properly before it gets to space is critical to its success," Young added. The report showed that technical issues, including human errors, have greatly impacted the development schedule. NASA has agreed to the review board's expert guidance on decisive steps necessary to safeguard and complete the telescope's development. In a message to the NASA workforce, NASA Administrator Jim Bridenstine said: "Webb is vital to the next generation of research beyond NASA's Hubble Space Telescope. "Despite major challenges, the board and NASA unanimously agree that Webb will achieve mission success with the implementation of the board's recommendations, many of which are already underway," Bridenstine noted. NASA previously had estimated an earlier launch date but the new launch date estimates to accommodate changes in the schedule due to environmental testing and work performance challenges by Northrop Grumman on the spacecraft's sunshield and propulsion system. The first telescope of its kind, and an unprecedented feat of engineering, Webb is at the very leading edge of technological innovation and development. From detecting the light of the first stars and galaxies in the distant universe to probing the atmospheres of exoplanets for possible signs of habitability, Webb's world-class science not only will shed light on the many mysteries of the universe, it also will complement and further enhance the discoveries of other astrophysics projects.