DUBLIN — A 24-hour strike at Irish airline Aer Lingus has grounded 202 flights and decimated traffic at the Republic of Ireland’s three main airports in a union dispute over work schedules.

Aer Lingus offered free refunds or rescheduled bookings to an estimated 28,000 passengers obstructed by Friday’s protest by the IMPACT trade union, which wants three-day breaks between work periods.

The airline has suffered repeated strike threats from its unionized staff as it seeks to compete with Dublin-based budget airline leader Ryanair.

IMPACT leaders say Aer Lingus sometimes makes flight attendants work six days in a row, with a single day off.