New Delhi, Feb. 14 -- One-day strikes by unions representing pilots and cabin crew at Lufthansa caused a wave of flight cancelations Thursday at Germany's biggest airline.

Lufthansa criticized the walkouts as disproportionate but said it expects to offer a largely normal flight program Friday.

Lufthansa said the strikes called by the Vereinigung Cockpit and UFO unions led to extensive cancelations, but didn't give a specific figure. The departures board at the airline's main Frankfurt hub suggested most of its flights from there Thursday morning were canceled.

The airline said it was trying to rebook passengers onto flights by partner airlines and other companies from the Lufthansa group, which includes airlines such as Swiss, Austrian...