A group affiliated with Islamic State has claimed responsibility for the crash of an Airbus A321 operated by a Russian carrier that was bringing holidaymakers home from a resort on Egypt's Sinai Peninsula.
All 224 people on board were killed in what the militants described as revenge for Russian air strikes in Syria that began more than a month ago.
While no official investigation has confirmed that claim of responsibility, countries have been cancelling flights and announcing new precautions, leaving tens of thousands of European and Russian tourists stranded at Red Sea resorts.
The US Department of Homeland Security announced new security measures on November 6, including tighter screening of items before they are brought on board aircraft, for flights to the United States from some foreign airports in the region.
US President Barack Obama and British Prime Minister David Cameron have already said the crash might have been caused by a bomb. Moscow initially rebuked Western countries for drawing such conclusions too quickly. But President Vladimir Putin's decision to suspend Russian flights suggests the Kremlin is no longer trying to avert attention from that theory.
White House spokesman Josh Earnest said the new US measures were a "prudent response" to boost security procedures already in place and will affect fewer than 10 airports.
All the airports being asked to tighten screening of US-bound flights are in the Middle East, a US official familiar with the matter said.
Decisions by Britain and other European countries to suspend flights to Sharm al-Sheikh left tens of thousands of tourists stranded in one of the most popular destinations for European holidaymakers seeking winter sunshine. Moscow's decision to follow suit November 6 adds tens of thousands more.