Flybe have been operating a return flight on Sundays on Sumburgh - Knock Ireland West- Sumburgh (Shetland Islands) I am not sure if it comes in on Saturday, but it takes off on Sunday morning. It's a direct flight.
I emailed asking for details and they said it was not possible to book a seat as it is a private charter. I thought that it was something to do with the detail of operating the Dublin Knock route for Aer Arann with Saab 340, but was advised that this has ended and the Sumburgh flight was separate totally.
Interesting to see Saab 340 into Knock, I think it takes off at 0915/0950.
EI-BUD