Beyonce is set to headline the festival on Sunday night, and according to reports, former bandmates Michelle Williams and Kelly Rowland could be joining her on stage.
A source told The Mirror, 'Originally the plan was simply for Kelly and Michelle to head down to Somerset to see their old bandmate.
'Beyonce was over the moon and sorted them out with access-all-area passes and accommodation.
'From there, plans developed and the idea of a brief on-stage Sunday evening reunion was mooted.
'It's still very much up in the air as no one wants Bey to feel she's being upstaged.
'One idea is for the two girls to join her on stage towards the end of her set for a medley of their hits. But whatever happens, the three girls are getting back together at Glasto and planning on having an absolute ball.'
The group split in 2004, and Kelly is currently working as a judge on the UK X Factor, while last year Michelle played Roxy in Chicago in the West End.