At least five bomb threats were made Tuesday against flights leaving from or landing in the United States, according to a report. <br /> <br />The threats, which were phoned in, were not deemed credible, NBC News reported, citing government sources. <br /> <br />It prompted a police bomb squad with search dogs to scour a US Airways flight when it landed at Philadelphia International Airport about 6:15 a.m. <br /> <br />Authorities had received a threat saying there were multiple devices aboard while the plane was en route from San Diego. <br /> <br />They found no signs a bomb was on the Airbus A320 carrying 88 passengers and five crew members. <br /> <br />Four of the five flights which received threats — from US Airways, Delta Air Lines, United Airlines and the Mexican carrier Volaris — have landed safely, according to NBC News. <br /> <br />A Korean Air Flight 23 from Seoul to San Francisco was scheduled to land Tuesday afternoon. <br /> <br />The hectic day for airliners was made worse when all United Airlines flights were temporarily grounded Tuesday morning for separate technical issues. <br /> <br />United delayed flights at 8 a.m. due to "automation issues." <br /> <br />The halt lasted about 39 minutes until officials could "ensure aircraft departed with proper dispatching information," United Airlines spokesman Charles Hobart said.
