Millions of dollars have been raised to construct a monument to honour the 40 passengers and crew of the hijacked Flight 93, which crashed in Shanksville.
It is believed that the passengers attempted to revolt against the terrorist hijackers just before the plane crashed.
The Flight 93 National Memorial commemoration ceremony will be held to officially announce the first phase of the monument's construction.
McLachlan's performance will be streamed live on the Flight 93 National Memorial website from 12.30pm ET on September 10.
More musical acts are expected to be announced in the coming days.
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Watch Sarah McLachlan sing 'Angel' below: