MONTGOMERY, Ala. — Four passengers have filed a lawsuit against Southwest Airlines, saying the company broke its contract with travelers by carrying them on planes that missed safety inspections over a period of about six years.

The lawsuit, filed Friday in federal court in Birmingham, seeks class-action status on claims that include breach of contract, unjust enrichment, and negligent and reckless operation of an aircraft.

Lew Garrison, a Birmingham lawyer who represents the passengers, said Tuesday the class could include hundreds of thousands of people who traveled on Southwest planes from January 2002 through last month. The lawsuit primarily seeks reimbursement for tickets for those flights on the grounds that the Dallas-based airline did not comply with government regulations and did not honor its contract with its customers.

The suit also seeks an unspecified amount in punitive damages on one count that claims Southwest behaved negligently in not grounding planes that had not been deemed airworthy.

Marilee McInnis, a spokeswoman for Southwest, said the company does not comment on pending litigation.