June 26 (Reuters) - Canada's WestJet Airlines has begun cancelling flights after a union representing its maintenance engineers rejected its new pay offer and served a second strike notice, the carrier said on Wednesday.

WestJet said this action would lead to an estimated 25 flight cancellations over June 27-28 and impact over 3,300 guests. (Reporting by Rishabh Jaiswal in Bengaluru; Editing by Janane Venkatraman )