Indian regulators have asked Kingfisher Airlines to explain why their license shouldn't be revoked as a strike forces the cash-strapped carrier to cancel flights through next Friday.

Kingfisher said late Friday that it would respond to the notice within 15 days and submit a "comprehensive plan for restoration of services after negotiations with our employees."

Flights have been grounded since Monday, as employees angry about not being paid for up to seven months refuse to work.

Civil Aviation Minister Ajit Singh said Friday that the carrier has passed all safety audits. Authorities have been criticized for not acting earlier to protect passengers from flight cancellations and the hazards of stressed pilots and engineers who haven't been paid in months.