Air Canada said on Tuesday that it will gradually restart operations after reaching a mediated agreement with its flight attendants' union.

Mediation discussions began on the basis that the Canadian Union of Public Employees (CUPE) committed to having the airline's 10,000 flight attendants immediately return to work, allowing Air Canada and Air Canada Rouge to resume operations after being grounded since Saturday, Canada's largest airline said in a news release.

"Restarting a major carrier like Air Canada is a complex undertaking. Full restoration may require a week or more," said Air Canada President and CEO Michael Rousseau.

According to the release, the first flights are scheduled for Tuesday evening, but customers are advised that the airline's return to full, regular service may take seven to 10 days.

During this process, some flights will be canceled over the next seven to 10 days until the schedule is stabilized, the release said.

The agreement provided some relief for the carrier, which usually carries about 130,000 customers a day, according to the airline.

Despite eight months of negotiations on issues including pay increases, ground pay, improved pensions and benefits, and longer crew rest periods, Air Canada has been unable to reach a tentative agreement with CUPE.