Spirit Airlines has nearly completed refunding customers after abruptly shutting down operations and canceling thousands of flights over the weekend.

The budget carrier said it was forced to fold after years of financial struggles and a sharp rise in jet fuel prices, which it says worsened its outlook.

The airline had already filed for bankruptcy twice and failed to secure new funding or a rescue deal.

Thousands of passengers and employees were left stranded as Spirit began an orderly wind-down process, The Guardian has reported.

The shutdown has sparked political blame, with officials pointing to past regulatory decisions and rising fuel costs as contributing factors.