By Lindsay Rogers Frontier and Spirit airlines have long helmed the discount carrier space, competing for lowest airfare — and most uncomfortable seats — for nearly three decades. But now, in a show of “if you can’t be more disappointing than them, join them” camaraderie, two of the most reviled names in the travel sector are finally joining forces. In a deal valued at $6.6 billion, executives at Spirit and Frontier have announced their intent to merge, creating — per a report from CNBC — what would be the 5th largest airline in the U.S. A super budget airline, if you will. Or a super shitty a…