Comparison of add-on charges by major US low-cost airlines

Baggage fees vary among the airlines. Allegiant charges between $10 and $75 for carry-on bags, with overweight bag fees ranging from $50 to $75 depending on weight. Spirit's carry-on fees range from $31 to $65, with overweight checked bag fees reaching up to $125. Frontier uses a Bag Price Checker tool to determine carry-on costs; overweight checked bags incur a fee of up to $100.

Priority boarding options are available with all three airlines at varying prices. Allegiant offers priority boarding for between $11.50 and $17.50, while Frontier's rates range from $.99 to $14.99 per direction.

For booking changes or cancellations, each airline has distinct policies and associated costs. Frontier allows free changes more than 60 days before departure but charges increase closer to the travel date unless bundled tickets are purchased. Allegiant offers Trip Flex to avoid most change fees; without it, cancellation results in credit minus certain charges.

Additional expenses include printed boarding passes—Allegiant charges $5 while Frontier's fee is significantly higher at $25—and pet transportation costs that vary across the airlines.

In-flight WiFi is only offered by Spirit Airlines at rates between $3.99 and $19.99 depending on usage needs; neither Frontier nor Allegiant provides this service currently.

The cost-effectiveness of flying with these carriers depends largely on the specific add-ons required by passengers since each airline has unique pricing structures for different services.

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