Israeli airstrikes hit Gaza, and Palestinian militants in Gaza fired rockets at targets in Israel, including the main airport in Tel Aviv.
United Airlines canceled flights from Chicago, Newark and San Francisco through Saturday. A spokeswoman said United will let customers booked on Tel Aviv flights through May 25 change their itineraries without paying a higher fare.
American Airlines canceled its daily flight from New York to Tel Aviv on Wednesday and Thursday and offered to put passengers on flights at later dates, according to an airline spokesman. Delta canceled flights from New York to Tel Aviv through Thursday.
Company representatives said the airlines were monitoring the situation for when they might resume the flights.