Lufthansa has been forced to cancel 800 flights on Tuesday as the spring of discontent among Europe's workers spreads to Germany.
The airline has axed half of its 1,600 scheduled flights, affecting 90,000 passengers.
Workers are staging the walkout ahead of pay talks, following similar action in France.
Air France is expected to face further disruption on Tuesday after industrial action at the weekend.
Lufthansa told passengers whose flights had not been cancelled to allow more time to travel and get to airports earlier.
The walk-out does not involve Lufthansa's own staff but public sector workers such as ground handlers at Frankfurt, Munich, Cologne and Bremen airports.
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.
Meanwhile, Air France said that it will operate 75% of its flights on Tuesday after grounding one third of services on Saturday.
Unions representing airline staff are demanding a 6% pay rise from the company, which is offering a 1% increase.
Rail travel in France is also under pressure amid ongoing strikes by SNCF staff in response to labour reforms under President Emmanuel Macron.