TUI has blamed the grounding of the 737 Max in a third-quarter briefing.
The airline, which has 15 Max aircraft, claimed in the latest financial results that the grounding will cost it approximately €300 million in the year ending 30 September.
The group's net profit declined 46% from the year prior to €47.3 million.
During the latest quarter, the group's EBITA declined 46% to €100.9 million from €186.8 million because of the 737 Max grounding.
Boeing is assuming the 737 Max will return to service in the US and other countries in the autumn. However, no firm date has been announced.
TUI Group, which has five airlines operating a 150-strong fleet, which includes 23 Max jets, posted a turnover rise of 3.7% to €4.75 billion.
TUI CEO Fritz Joussen said: “Despite the challenging environment in 2019 to date, our underlying business remains robust, and we expect to deliver a solid performance in 2019, which, however, will not match the prior year’s result, as expected due to the grounding of the 737 Max.”