The blending of Allegiant Air and Sun Country Airlines sailed through the merger process because the two air carriers are so similar and because there was almost no overlap between the companies’ routes, a top Allegiant executive said Thursday. Allegiant President and Chief Financial Officer Robert “BJ” Neal said there’s still plenty of work ahead to integrate the two airlines that on Wednesday officially merged and will be headquartered in Las Vegas. “We’re trying to balance between celebrating, because it is quite a big feat, but also keeping in mind we’ve got a lot of work ahead of us as well,” Neal said in an exclusive interview with the Las Vegas Review-Journal. The $1.5 billion merger between Allegiant and Minneapolis-based Sun Country was first announced Jan. 11, making the time between announcement and closing the deal just over four months, practically unheard of in the airline industry.…