Pilots at German carrier Lufthansa began a two-day strike Monday, causing major disruptions to flights across the airline and several subsidiaries at a time when the conflict in the Middle East already strains the air travel industry.

The walkout by pilots at Lufthansa's core brand, as well as Lufthansa Cargo and Lufthansa CityLine, began shortly after midnight Monday and will last for 48 hours.

At holiday airline Eurowings, all departures from German airports will be affected Monday only.

Hundreds of flights are set to be canceled Monday and Tuesday, with Lufthansa's hubs in Frankfurt and Munich hardest hit.

The strike marks the fourth wave of industrial action at the group this year. Last week, a one-day cabin crew walkout forced hundreds of cancellations at Germany's largest airline.

The pilots' strike, organized by the Vereinigung Cockpit union, centers on pay disputes, including the company pension scheme and remuneration at the regional subsidiary CityLine.

Lufthansa criticized the union's strike notice, saying it represented a new level of escalation.

Flights to selected Middle Eastern destinations have been excluded from the strike action.