According to their website, AviaJet are a British charter broker
In the UK they represent Spanair, EuroAtlantic, Air Mediterranee and Panair.
They also offer 1 B767-300ER and 1 MD-82 for charter flights, which are operated on their behalf by Icelandic carriers. The B767 is operated by Air Atlanta, I'm assuming the MD-82 is operated by MD Airlines, I don't know of any other Icelandic MD- operators.
So it isn't actually an airline at all!!!