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 announcement comes before the busiest travel weekend, Thanksgiving, but the airline assured its customers that the tickets they booked are still active and future fares will also be.

Budget carrier Spirit Airlines has filed for bankruptcy protection after years of financial losses and failed merger attempts. On Monday, the airline said it had filed a Chapter 11 bankruptcy petition after working out terms with bondholders.