Israel hit more than 1,000 targets in Gaza and Palestinian militants continued firing barrages of rockets, setting off air raid sirens in Jerusalem and Tel Aviv. Video posted online appeared to show a plume of smoke near a terminal at Tel Aviv’s Ben Gurion International Airport.

Scores of arriving and departing flights at Ben Gurion were canceled or delayed, according to the airport’s online flight board, which also showed a steady trickle of flights. Most were operated by Israel’s national airline El Al along with others by regional carriers like Turkey’s Pegasus Airlines and Greece’s Blue Bird Airways.

American Airlines, United Airlines and Delta Air Lines suspended service as the U.S. State Department issued travel advisories for the region citing potential for terrorism and civil unrest.

American suspended service to Tel Aviv through Friday. The airline said that it has issued a travel alert providing additional flexibility for customers whose travel plans are impacted.

“We continue to monitor the situation with safety and security top of mind and will adjust our operation as needed,” American said.

United said it allowed two scheduled flights out of Tel Aviv late Saturday and early Sunday and accommodated its customers, crews and employee travelers who were at the airport. The airline said that its Tel Aviv flights will remain suspended until conditions improve.

Delta said its Tel Aviv flights have been canceled into this week. The airline said it’s monitoring the situation and making schedule adjustments accordingly. The company said customers with canceled flights or who want to change their Tel Aviv ticket should check the Delta app, website or call Delta reservations to make adjustments.

Airlines in Europe and Asia also put flights on hold amid the hostilities, offering refunds and waiving rebooking fees for passengers.

Air France said that it has suspended services to Tel Aviv “until further notice” after coordinating with French and Israeli authorities.

“The airline is constantly monitoring the geopolitical situation in the areas served and overflown by its aircraft in order to ensure the highest level of flight safety,” Air France said in on its website.

Germany’s Lufthansa, which suspended flights to and from Tel Aviv until Saturday, said Monday that the decision regarding its planes and those of its subsidiaries was made “due to the still unclear developing security situation in Israel and after an intensive analysis of the situation.”

The Lufthansa Group includes Austrian Airlines, Swiss and Brussels Airlines as well as Lufthansa itself.

Hong Kong’s main carrier, Cathay Pacific Airways, said that “in view of the latest situation in Israel,” it was cancelling its Tel Aviv flights scheduled for Tuesday and Thursday.

“The safety of our passengers and crew are our top priority. We will continue to monitor the situation very closely,” the airline said on its website, adding it would provide another update on Friday ahead of its third weekly flight on Sunday to the Israeli city.

Virgin Atlantic canceled its service between London’s Heathrow Airport to Tel Aviv on Monday and Tuesday as well as part of that route on Wednesday.

Budget airline Wizz Air, which flies to Israel from Abu Dhabi and more than two dozen airports in Europe, said it was cancelling all flights to and from Tel Aviv “until further notice.”

The U.K. discount carrier easyJet said that “due to the evolving situation in Israel,” it has decided to “temporarily pause operations,” by canceling its Monday flights from London Luton and Manchester airports to Tel Aviv.

“Our thoughts are with those who have been affected and the safety and security of our passengers and crew is always easyJet’s highest priority,” easyJet said in a statement.

British Airways said it’s planning to continue operating flights to Israel “over the coming days with adjusted departure times.”

Dutch carrier KLM said it’s scrubbing flights to Tel Aviv “until and including Wednesday.”

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AP Business Writer Kelvin Chan contributed to this report from London. AP Writer Geir Moulson contributed from Berlin. AP Writer David McHugh contributed from Frankfurt.