Lufthansa cabin crew are planning to stage a second round of strikes on 4 September.
German flight attendant union UFO - which began its industrial action in Frankfurt on 31 August - says it will continue the walkouts because Lufthansa has not signalled any movement in stalled wage negotiations.
UFO has not revealed where the next round of strikes will take place, but it says the action will include other locations and extended periods of disruption.
The union plans to reveal details at least six hours before the next walkout begins.
Cabin crew staged the first round of strikes in Frankfurt between 05:00 and 13:00 on 31 August, prompting flight cancellations and delays throughout the weekend.
UFO says the airport had to be temporarily closed as aircraft were unable to leave their gate positions, which forced several hundred passengers to sleep in the terminal.
Five flights have already been cancelled for 3 September due to the knock-on effect of last week's walkout.