| Clue | Source | Date |
|---|---|---|
| 1975 U.S.-USSR space mission whose second word is Russian for "union" | ||
| 1970s joint U.S.-Soviet space flight | LA Times Daily | 19 Nov 2019 |
| 1970s joint U.S.-Soviet space flight | The Washington Post | 19 Nov 2019 |
| 1970s joint U.S./Soviet space project | ||
| First joint flight of the U.S. and Soviet space programs |