Boeing Co.’s aircraft delivery delays are affecting passenger growth projections at Frankfurt airport because the main airline at the hub, Deutsche Lufthansa AG, isn’t getting the aircraft it had planned for this year. 

Passengers numbers are set to come in at the lower end of a range of 61 million to 65 million travelers this year, the airport operator said in a statement on Tuesday as it reported earnings. Growth also slowed sequentially this year, with passenger numbers up 4.5% in the second quarter, compared with a 10.4% increase in the first three months, the company said. 

Lufthansa is the biggest carrier at Germany’s largest hub, meaning that any issues at the airline feed through to the airport. Lufthansa said last week that it won’t get any new Boeing 787 Dreamliners this year. Some of its Airbus SE aircraft also require extra maintenance on engines, affecting growth plans. 

Fraport Chief Executive Officer Stefan Schulte said high costs imposed by German regulators have also constrained growth. While Boeing has curbed production to improve manufacturing quality, Airbus has cut its annual delivery target because of a shortage of parts. Those setbacks have left some airlines unable to grow as quickly as they had planned.

Lufthansa trimmed its profit outlook a few weeks ago for this year, partly because of inefficiencies in its flight operations prompted by the delayed jets. The company is still waiting for Boeing’s 787 Dreamliners and the 777X to join its fleet and replace older aircraft.