The latest strike by Lufthansa pilots grounded almost 900 flights on Wednesday and German companies and other Lufthansa staff called for an end to the protests which are costing the airline 10-15 million euros a day.
Pilots staged a four-day strike last week then resumed their protest over pay that dates back to early 2014 on Tuesday, taking the number of cancelled flights in the latest round of walkouts to about 4,500.
One of Lufthansa's major corporate customers, Siemens, said the strikes were harming the Germany economy and the country's image and warned Lufthansa that it needed to become more reliable.
"As a major customer we have to consider how we can deal with this on a long-term basis," Siemens CEO Joe Kaeser told German daily Bild, adding that the pilots should resume talks.
Analysts have said the walkouts are a good opportunity for rivals such as Ryanair and easyJet to gain market share and could mean Lufthansa misses its 2016 profit target. Its shares dropped 2.7 percent on Wednesday.
The pilots' union Vereinigung Cockpit (VC) is due to hold a rally at Frankfurt airport on Wednesday morning.
While the union has been tweeting messages of support from other pilot unions around the world, the officers will face a counter-demonstration from Lufthansa ground crew, who feel the pilots are hurting the company and endangering jobs.
However, there could be movement in the dispute after the union said it was willing to compromise. A Lufthansa spokesman said the airline was considering comments by VC that it would resume talks if a pay increase of about 5 percent were used as a basis for negotiations.
Lufthansa has offered to raise pilots' pay by 4.4 percent in two instalments and make a one-off payment worth 1.8 months' pay.
VC wants an average annual pay rise of 3.7 percent for 5,400 pilots over a five-year period backdated to 2012.
The strike is the 15th since early 2014. Walkouts in 2015 by both pilots and cabin crew affected 7,748 flights, costing Lufthansa 231 million euros in lost profit, with around 108 million of that coming from lost advance bookings.