The Dangerous Woman singer was set to be a special guest at the U.K. awards show during a tribute performance in remembrance of the tragedy that took place outside of her 2017 concert in England, but had to pull out due to health reasons that kept her from flying, a source tells ET.
"Ariana fell ill and was going to come in spite of that, but was ordered by her doctor to not fly," the source explains.
The BRIT Awards take place on Wednesday.
After the terror attack, Grande put together "One Love Manchester," a star-studded benefit concert that raised millions of dollars for the Red Cross' We Love Manchester emergency fund. For her efforts to help the victims' families after the tragedy, the 24-year-old singer was made an honorary citizen of Manchester last July.