Spirit Airlines, the scrappy discounter that once rattled the industry with cheeky ads and rock-bottom fares, took its final flight after 34 years of upending the business of flying. Once worth as much as roughly $5.5 billion on the stock market, the airline known for its bright yellow planes said Saturday it had shut down after its final flight departed from Detroit and landed safely in Dallas. “For more than 30 years, Spirit Airlines has played a pioneering role in making travel more accessible and bringing people together while driving affordability across the industry,” CEO Dave Davis said in a statement. The announcement comes after two bankruptcy filings in as many years that allowed Spirit to repay lenders. That was followed in recent months by a final, mad-dash scramble to save money by cutting routes, squeezing concessions from unions and pursuing a potential financing deal with the Trump administration that could have provided a lifeline had it panned out.…