The lease of Sunwing aircraft by Thomson was probably on the cards even before the closure of Skyservice, it's just happened a year or two sooner.
In September 2009, TUI and Sunwing agreed to effectively merge their operations in Canada;
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The prospect of the impending end of the old First Choice/Skyservice agreement probably cemented the idea in the Skyservice management's mind that the business wasn't viable anymore when Thomas Cook called in their debt, in the peak season most of Skyservice's aircarft (and business) was supplied by their 2 European counterparts.