Led Zeppelin is turning the aggression up to 11 in a copyright infringement lawsuit brought against the group over its classic song “Stairway to Heaven.”

Lawyers for Robert Plant, Jimmy Page and John Paul Jones have fired off a blistering opposition to plaintiff Michael Skidmore’s application to modify the scheduling order for the case.

In the legal papers filed last week, Team Zep accuses Skidmore’s side of dragging its feet, then demanding more time at the 11th hour, with the cut-off for discovery in the case set for Thursday.

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“Plaintiff filed this action on the District Court in Pennsylvania on May 31, 2014, and it was transferred here on May 18, 2015,” the opposition, filed in federal court in California, reads. “Since then, and since the Court’s Scheduling Order, plaintiff has done little to prosecute this case and defendants’ discovery has confirmed his claim is baseless. Now, on th e eve o f next Thursday’s discovery cut-off, he seeks the Court’s intervention to provide him more time to pursue that baseless claim. His application should be denied.”

Zeppelin’s lawyers say that the request is particularly inconvenient for former Zep vocalist Robert Plant, who cleared his tour schedule for the scheduled May trial based on the scheduling order.

The opposition also rips into Skidmore’s request for the original multi-track tapes of the “Stairway to Heaven” recording for “further musical analysis,” saying that they’re not relevant to the case.

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“Forty-five-year-old, original analog multi-tracks — which are fragile and extremely valuable — that have never been publicly distributed or commercially exploited, are simply not relevant in this action,” the filing reads.

Skidmore alleges that “Stairway to Heaven” infringes on the Spirit song “Taurus.” Skidmore is suing in his capacity as the trustee of the Randy Craig Wolfe Trust. (Spirit leader and “Taurus” author Randy California’s birth name was Randy Craig Wolfe. Wolfe is deceased.)

Pamela Chelin contributed to this report.

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