Italian state airline Alitalia canceled 12 flights at short notice due to cabin crew shortages on Sunday, leaving some travelers stranded.
The airline said it had canceled 10 international and two domestic flights out of Rome's Leonardo Da Vinci airport, and that other flights had been delayed.
Alitalia said some cabin crew had not shown up for work for reasons that were not immediately clear.
Paolo Maras from transport labor union SULT said staff were overstretched because Alitalia had not provided for cabin crew quotas agreed on in workers' contracts.
Maras also said Alitalia had failed to hire enough extra cabin crew staff to cover busy summer schedules.
On Saturday, Alitalia canceled 196 flights during a four-hour walkout by air traffic controllers, the second such strike this month.