Good question! According to a NASA scientist, Dr. Eric Christian, all of the planets in our solar system have probably never lined up on an “exact” line planets align

However, they probably have been arranged in a “rough” line before, and this probably only happens once in millions of years

Though not all of the planets have lined up any time recently, several of them have in the recent past. In 2000 the moon, Mercury, Venus, Mars, Jupiter, and Saturn came pretty close to lining up. In 1962 the Sun, Moon, Mercury, Venus, Earth, Mars, Jupiter, and Saturn came really close to lining up. It turns out that the five these planets come close to lining up about every 57 years!