Budget carrier Spirit Airlines announced it filed for Chapter 11 bankruptcy on Monday in the face of mounting losses, increased labor costs and a highly competitive air travel market. The airline has failed to return to profitability following the downturn in air travel caused by coronavirus pandemic lockdowns.

The airline listed its estimated assets and liabilities in the range of $1 billion to $10 billion each, according to a court filing on Monday.

The company has reassured passengers that its Chapter 11 bankruptcy will not affect their bookings and that staff will still be paid.

The disparity in size between the low-priced airlines and the top firms underscores a fissure in the industry separating budget carriers in select markets from the major airlines that dominate flight offerings nationwide, Mike Boyd, president of aviation consulting firm Boyd Group International, told ABC News.

Spirit Airlines said Monday that it's filed for bankruptcy protection and will attempt to reboot as it struggles to recover from the pandemic -caused swoon in travel and failed attempts to sell itself to other carriers.

NEW YORK -- Spirit Airlines, the largest budget carrier in the U.S., filed for Chapter 11 bankruptcy protection Monday. The airline said customers should not see any disruption to their travel plans while the process unfolds.