Editing Lockheed U-2 (section)

====Renewal of Eastern Bloc overflights====
Eisenhower refused CIA pleas in September 1956 to reauthorize overflights of Eastern Europe but the [[Hungarian Revolution of 1956|Hungarian Revolution]] in November, and [[1956 United States presidential election|his reelection that month]], caused the president to permit flights over border areas. Soviet interceptors could still not reach the U-2s but, after the Soviets protested a December overflight of Vladivostok by RB-57Ds, Eisenhower again forbade communist overflights. Flights close to the border continued, now including the first [[ELINT]]-equipped U-2s. In May 1957, Eisenhower again authorized overflights over certain important Soviet missile and atomic facilities. He continued to personally authorize each flight, closely examining maps and sometimes making changes to the flight plan.{{sfn|Pedlow|Welzenbach|1992|pp=122–124, 126–128}} By 1957, one of the European units was based at Giebelstadt, and the far eastern unit was based at the [[Naval Air Facility Atsugi]], Japan.<ref name="CIA0000743239">[http://www.foia.cia.gov/sites/default/files/document_conversions/89801/DOC_0000743239.pdf "Future Plans for Project AQUATONE/OILSTONE."] {{Webarchive|url=https://web.archive.org/web/20140201191253/http://www.foia.cia.gov/sites/default/files/document_conversions/89801/DOC_0000743239.pdf |date=1 February 2014 }} ''Central Intelligence Agency'', 29 July 1957, p. 2. Retrieved: 12 June 2010.</ref>

Part of the reason for the May reauthorization was that the CIA promised that improvements from Project RAINBOW would make the majority of U-2 flights undetected. On 2 April 1957, a RAINBOW test flight crashed in Nevada, killing the pilot. The U-2's large wingspan slowed its descent during crashes, often leaving its remains salvageable; Lockheed was able to rebuild the wreckage from the incident into a flyable airframe, but that it could do so should have been evidence to the CIA that its cover story might not be viable after a crash in hostile territory. The RAINBOW anti-radar modifications were not very successful, and their use ended in 1958.{{sfn|Pedlow|Welzenbach|1992|pp=128–133}}

Soviet overflights resumed in June 1957 from [[Eielson Air Force Base]] in Alaska to the [[Russian Far East]], which had less effective radar systems. Others originated from [[Lahore, Pakistan]]. A Lahore flight on 5 August provided the first photographs<ref>{{cite journal |last1=Gruntman |first1=Mike |title=From Tyuratam Missile Range to Baikonur Cosmodrome |journal=Acta Astronautica |date=1 February 2019 |volume=155 |pages=350–366 |doi=10.1016/j.actaastro.2018.12.021 |url=https://www.sciencedirect.com/science/article/abs/pii/S009457651831751X |location=Fig.7 |bibcode=2019AcAau.155..350G |s2cid=116406451 |language=en |issn=0094-5765 |access-date=22 February 2020 |archive-date=18 October 2021 |archive-url=https://web.archive.org/web/20211018220959/https://www.sciencedirect.com/science/article/abs/pii/S009457651831751X |url-status=live |url-access=subscription }}</ref> of the [[Baikonur Cosmodrome]] near [[Tyuratam]]: the CIA had been unaware of its existence until then. Other flights examined the [[Semipalatinsk]] nuclear test site and the [[Saryshagan]] missile test site.{{sfn|Heppenheimer|1998|p=193}}{{sfn|Pedlow|Welzenbach|1992|pp=135–139}} After a few more overflights that year, only five more took place before the May 1960 incident because of Eisenhower's increasing caution. The president sought to avoid angering the Soviets as he worked to achieve a [[Partial Nuclear Test Ban Treaty|nuclear test ban]]; meanwhile, the Soviets began trying to shoot down U-2 flights that never entered Soviet airspace, and the details in their diplomatic protests showed that Soviet radar operators were able to effectively track the aircraft. To reduce visibility Lockheed [[military camouflage|painted the aircraft in a blue-black color]] that helped them blend in against the darkness of space, and the CIA aircraft received the more powerful [[Pratt & Whitney J75-P-13]] engine that increased maximum altitude by {{convert|2500|ft|m|-2}}, to {{convert|74600|ft|m|-2}}.{{sfn|Pedlow|Welzenbach|1992|pp=143–144, 147–152}} In April 1958, CIA source [[Pyotr Semyonovich Popov]] told his handler [[George Kisevalter]] that a senior KGB official had boasted of having "full technical details" of the U-2, leading Bissell to conclude the project had a leak. The source of the leak was never identified, although there was speculation that it was [[Lee Harvey Oswald]], then a radar operator at a U-2 base in Japan.<ref>{{cite book|last=West|first=Nigel|url=https://books.google.com/books?id=0eAHTaMMP6QC&pg=PA350|title=Historical Dictionary of Cold War Counterintelligence|year=2007|publisher=[[Scarecrow Press]]|isbn=978-0-8108-6463-4|page=350}}</ref>

The Soviets developed their own overflight aircraft, variants of the [[Yakovlev Yak-25|Yak-25]], which in addition to photographing various parts of the world through the early 1960s acted as a target for the new [[Mikoyan-Gurevich MiG-19|MiG-19]] and [[Mikoyan-Gurevich MiG-21|MiG-21]] interceptors to practice for the U-2.