The Airline with the Best Customer Satisfaction Is …

The latest issue of the DOT’s “Air Travel Consumer Report,” released this week, showed an uptick in March traveler complaints, both over the previous month and over March 2014.

Year over year, complaints for the month were up 55 percent. Frontier and Spirit were the worst and second worst, with 16 and 10 complaints per 100,000 enplanements, respectively. Southwest was best, with just 0.46 complaints per 100,000 enplanements.

The complete list, from best to worst:

• Southwest
• Alaska
• Skywest
• ExpressJet
• Delta
• Virgin America
• JetBlue
• Hawaiian
• Envoy
• United
• American (including US Airways)
• Spirit
• Frontier

Spirit and Frontier also ranked at or near the bottom of the list for on-time arrivals for the month.

Both Spirit and Frontier are ultra-low-cost carriers. But the similarities run much deeper. Indigo Partners, which owns Frontier, is headed by Bill Franke, the former chairman of Spirit. Both companies boast low fares, surcharges for any- and everything, and bare-bones service.

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That’s a formula that has served both companies well, financially speaking. Customer satisfaction? Not so much.

Reader Reality Check

Are you a fan of Spirit or Frontier?

This article originally appeared on FrequentFlier.com.