Editing Sound barrier (section)

===The sound barrier understood===
[[Image:Yeager supersonic flight 1947.ogv|thumb|[[Chuck Yeager]] broke the sound barrier on 14 October 1947 in the [[Bell X-1]], as shown in this newsreel.]]

As the science of high-speed flight became more widely understood, a number of changes led to the eventual understanding that the "sound barrier" is easily penetrated, with the right conditions. Among these changes were the introduction of thin [[swept wing]]s, the [[area rule]], and engines of ever-increasing performance. By the 1950s, many combat aircraft could routinely break the sound barrier in level flight, although they often suffered from control problems when doing so, such as [[Mach tuck]]. Modern aircraft can transit the "barrier" without control problems.<ref>[https://web.archive.org/web/20180922211527/http://www.diracdelta.co.uk/science/source/s/o/sound/ barrier/source.html "Sound Barrier"]. ''DiracDelta.co.uk: Science and Engineering Encyclopedia''. Retrieved: October 14, 2012.</ref>

By the late 1950s, the issue was so well understood that many companies started investing in the development of supersonic airliners, or [[Supersonic transport|SSTs]], believing that to be the next "natural" step in airliner evolution. However, this has not yet happened. Although the [[Concorde]] and the [[Tupolev Tu-144]] entered service in the 1970s, both were later retired without being replaced by similar designs. The last flight of a Concorde in service was in 2003. Despite a resurgence of interest in the 2010s, as of 2024 there are no commercial supersonic airliners in service.<ref>{{Cite news |date=2024-03-18 |title=See what's fueling the return of supersonic passenger flights |url=https://www.washingtonpost.com/business/2024/03/18/supersonic-plane-travel-passenger-jet/ |access-date=2024-05-17 |newspaper=Washington Post |language=en}}</ref>

Although Concorde and the Tu-144 were the first aircraft to carry commercial passengers at supersonic speeds, they were not the first or only commercial airliners to break the sound barrier. On 21 August 1961, a [[Douglas DC-8]] broke the sound barrier at Mach&nbsp;1.012, or 1,240&nbsp;km/h (776.2&nbsp;mph), while in a controlled dive through 41,088&nbsp;feet (12,510&nbsp;m). The purpose of the flight was to collect data on a new design of leading edge for the wing.<ref>[http://www.dc8.org/library/supersonic/index.php "Douglas Passenger Jet Breaks Sound Barrier"] {{Webarchive|url=https://web.archive.org/web/20061026041859/http://www.dc8.org/library/supersonic/index.php |date=2006-10-26 }}. ''dc8.org''. Retrieved: August 30, 2010.</ref>