Air Berlin said flights to Tel Aviv remain suspended at least through midday Friday, while Lufthansa said all Friday flights to the airport have been canceled because of ongoing security concerns after a Hamas missile landed near it this week.
Lufthansa said flights will resume "as soon as this protection can be verifiably guaranteed."
Lufthansa's cancellations apply to subsidiaries Germanwings, Austrian Airlines, Swiss and Brussels Airlines as well, AP reported.
This comes as the 18-day Israeli offensive on Gaza has so far claimed the lives of at least 816 Palestinians, including scores of innocent children, according to the health ministry in Gaza.
More than 5,200 others have been reported injured.
Israel claims that its large-scale strikes on the besieged Gaza Strip are targeting Hamas fighters and a network of underground tunnels but most of those killed in Gaza were civilians, including scores of children.
At least 15 Palestinians died after a UN facility in Gaza sheltering displaced people was hit by Israel on Thursday.