In a decision on Friday, US district judge Gary Klausner in Los Angeles said the song and the 1967 instrumental Taurus by the band Spirit were similar enough to let a jury decide whether Plant and Page were liable for copyright infringement.
A trial is scheduled for 10 May.

The lawsuit was brought by Michael Skidmore, a trustee for the late Randy Wolfe, also known as Randy California, who was Spirit’s guitarist and the composer of Taurus.
Skidmore said Page may have been inspired to write Stairway to Heaven for Led Zeppelin after hearing Spirit perform Taurus while the bands toured together in 1968 and 1969, but that Wolfe never got credit.
The defendants said Wolfe was a songwriter-for-hire who had no copyright claim, and that the chord progressions were so clichéd that they did not deserve copyright protection.
But the judge said a jury could find “substantial” similarity between the first two minutes of Stairway to Heaven and Taurus, which he called “arguably the most recognizable and important segments” of the songs.

“While it is true that a descending chromatic four-chord progression is a common convention that abounds in the music industry, the similarities here transcend this core structure,” Klausner wrote. “What remains is a subjective assessment of the ‘concept and feel’ of two works ... a task no more suitable for a judge than for a jury.”

Klausner dismissed claims against Led Zeppelin bassist John Paul Jones and Warner Music Group.  He also said the trustee could get only 50% of any damages awarded, citing a 1967 contract that Wolfe signed.
“This case, from our perspective, has always been about giving credit where credit was due, and now we get to right that wrong,” said Francis Malofiy, a lawyer for Skidmore.  A lawyer for the defendants did not immediately respond on Monday to requests for comment.

According to the complaint, Wolfe complained about the similarities of the songs in an interview shortly before he drowned in 1997 in the Pacific Ocean while attempting to rescue his son.