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 | This timeline of spaceflight may require cleanup to ensure consistency with other timeline of spaceflight articles. See Wikipedia:WikiProject Spaceflight/Timeline of spaceflight working group for guidelines on how to improve the article. Details |  |
 Soyuz-U launch vehicle | |
| Orbital launches | |
|---|---|
| First | 5 January |
| Last | 2 December |
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On 29 March 1974 Mariner 10 became the first spacecraft to fly by Mercury, that saw a spacecraft for the first and last time in the 20th century.