When the delay on his 90-minute flight stretched past the four-hour mark, David Rankin started tweeting to Spirit Airlines as he and other passengers grew restless.

“We’re looking at the plane,” Rankin said by phone from a Spirit gate at the Philadelphia airport. “There are no pilots.”

Rankin, an investment manager from New Jersey, swore it would be his last time on the discount airline. “My wife won’t let me book a flight on Spirit next time,” he said.

Spirit is one of a new breed of airline called ultra-low-cost carriers that also includes Frontier Airlines and Allegiant Air. They have grown rapidly by luring travelers with cheap base fares that undercut the big airlines, and boast among the best operating profits margins in the business.

Fans say the cheap tickets set the ultra-low-cost carriers apart in an industry where discomfort and inconvenience are now expected. But for many travelers, the new discounters take the aggravation to another level.

They charge extra for things that are still standard on bigger airlines like soda and carry-on bags. Need to print a boarding pass at the airport? There’s a fee for that. They fit more passengers on the plane by squeezing seats together, which is easier because the seats don’t recline. They don’t have toll-free phone numbers for customer service.

There are few businesses that consumers love to hate more than airlines, but travelers seem to reserve a special level of vitriol for these no-frills, discount airlines.

Passengers are about 20 times more likely to complain about one of them than about Alaska Airlines or Southwest Airlines, which have the industry’s lowest complaint rates. Either Frontier or Spirit has recorded the highest rate of complaints to the government every month this year. Allegiant would place third-worst, although because of its small size it is not included in the official rankings.

Much of the grousing can be tied to frequent flight delays. So far this year, Spirit Airlines has the worst on-time rate among the largest 14 U.S. airlines — 34 percent of flights are at least 15 minutes late — and Frontier is next-to-last.

In June, Spirit’s on-time rate tumbled below 50 percent. It was the worst one-month performance by a large U.S. airline in 10 years. A Spirit spokesman blamed a four-day stretch of bad weather.

With fewer planes and pilots, Spirit, Frontier and Allegiant have less flexibility to deal with setbacks like summer storms than do larger airlines — it’s not as easy to put passengers on a later flight because there might not be one. They generally don’t have agreements to accommodate stranded passengers on bigger airlines. It can add up to long delays as crews try to wait out the weather or fix planes to avoid canceling flights.

In June, several hundred Spirit passengers were stuck at the airport in Las Vegas after cancelations. Airport officials handed out water and diapers. The same month in Atlantic City, New Jersey, two state troopers bought 15 pizzas to feed stranded Spirit passengers whose flight had been diverted there because of bad weather.

Another source of irritation: tight legroom. Frontier added 12 seats to its current planes by installing seats with less padding. Its new Airbus A321 jets arriving next year will have 230 seats. Spirit flies the A321 with 218 seats, JetBlue with 190, American with 181.

Unhappy customers also complain about being nickel-and-dimed — all the fees offset the cheaper base fare.

Heidi Kerr-Schlaefer, a Colorado travel writer, said she was a loyal customer of Denver-based Frontier Airlines for more than a decade. She “loved, loved, loved” the hometown airline with its wild-animal logos and friendly staff. But when the airline switched to mimic Spirit’s low-fare, high-fees model last year, calculating the cost of a trip got too complicated.

“I had to sit down and say: This is what I’m paying for the flight, then they’re charging me $3 or $5 for a seat (assignment), and I need to figure out how much baggage I’ll bring both ways,” she said. “It became a mathematics game and that’s ridiculous.”

The discount airlines, however, have their fans. Traffic jumped 77 percent on Spirit and 39 percent on Allegiant from 2011 through 2014. Travel is up by double-digits again this year on both airlines.

Even passengers on other airlines might owe the discounters some gratitude. By keeping base fares low, they prevent the major airlines from pushing prices even higher — at least on the routes they compete on — says John Kwoka, a Northeastern University economics professor who studies the airlines.

Loyal customers say you can avoid most fees and save money on the budget carriers if you pay attention to the rules.

“I’ve been on American Airlines, Frontier, Spirit — it’s all the same as long as I get to where I need to be,” Larry D. Wallace, a college student from Dallas, said on a recent Spirit flight from Dallas to Denver. “I’ve never had a complaint with Spirit. They’re cheap; they’re on time.”

Wallace, who said it was his fourth trip on the budget carrier, saved money by not bringing a bag. And his flight was just about perfect. The Airbus A320 was clean and brand-new — Spirit’s fleet averages about five years in age, much younger than most U.S. airlines — the flight attendants were cheerful and efficient. The flight arrived in Denver 15 minutes late, but no one seemed to mind.

Executives at the discount airlines and some industry experts dismiss the government’s complaint figures. They point out that very few passengers bother to file a complaint with the Department of Transportation — even at Spirit and Frontier it’s fewer than one passenger in every 10,000.

That can make for volatile figures. But ironically, by the airlines’ own admission, the government numbers don’t tell the full story of passenger unhappiness.

Frontier CEO Barry Biffle says his airline gets about 30 complaints for every one filed with the government. It used to 90-to-1, he says.

Biffle says the official complaint rate just measures how many customers find the website to lodge a complaint and they’re getting more savvy about that. But if airlines had to report all the complaints that they receive directly from consumers, the numbers would be even more damning.

(AP)