Lufthansa and Air France flights grounded by strikes

Frankfurt is among the airports affected by the strike

Two of Europe's biggest airlines have been hit by strike action, grounding hundreds of flights and affecting tens of thousands of passengers.

Lufthansa has been forced to cancel 800 of its 1,600 scheduled flights because of a walkout by public sector workers.

The stoppage is in force at Frankfurt, Munich, Cologne and Bremen airports.

At the same time, Air France has cancelled one in four of its flights as airline staff take action in support of a 6% pay claim.

Lufthansa has said about 90,000 passengers have been hit by the German public sector strike, which does not involve the airline's own staff.

Lufthansa told passengers whose flights had not been cancelled to allow more time to travel and get to airports earlier.

'Unacceptable' action

The trade union Verdi said the strikes were intended to "increase pressure" on public sector employers ahead of wage talks.

However, Lufthansa said it "cannot comprehend Verdi's threat to carry out such a massive strike".

"It is completely unacceptable for the union to impose this conflict on uninvolved passengers," said Bettina Volkens, Lufthansa's head of human resources.

"Lufthansa is not a part of this collective bargaining conflict, but unfortunately our customers and our company are being affected by the consequences of this dispute."

She added: "Politicians and legislators must define clear rules for strikes and industrial actions."

Lufthansa said normal services would resume on Wednesday.

Labour reforms

Meanwhile, Air France has said that it faces costs of €170m (£148m) from a wave of strike action by its employees, of which Tuesday's stoppage is merely the latest example.

The strike is set to continue on Wednesday, with further walkouts planned on four more days this month.

Rail travel in France is also under pressure from a rolling programme of strikes by SNCF staff, in response to labour reforms under President Emmanuel Macron.