VS21 Aircraft Change

Can anyone tell me why the VS21 LHR - IAD has been flying the new 787-9 Dreamliner since February and this last week has changed to an older Airbus 330 ?
We are flying out at end of April and we're hoping to be lucky enough to be able to get the Dreamliner experience.
Is it having a rest for maintenance or being used on another route now ?

It was only on the IAD route until the end of the winter timetable last weekend.

Dreamliners have now been moved to other routes. There's a list in this thread: http://v-flyer.com/forum/index.php?f=4& ... &start=460

Looks like it'll be back on the VS21/22 next winter, at least on certain days of the week.

Oh well.
Thanks for the quick reply