Aer Rianta has said that all three State airports - in Dublin Cork and Shannon - will be on a heightened security status following today's terrorist attacks in the US. Aer Lingus, in a statement, said that all its transatlantic flights tomorrow inbound and outbound had been cancelled.
One Aer Lingus flight today diverted to Canada and two others turned back to Dublin. A number of other flights from other countries heading for the US were diverted to Ireland. Five flights were diverted to Shannon.
Delta Airlines have cancelled flights to New York and Atlanta tomorrow (Wednesday). Passengers are asked not to turn up at either Shannon or Dublin airports but to call 1800 768 080 instead.
Aer Rianta says it is unclear when flights to the US will resume or when passengers stranded in the US will be able to return to Ireland.
In Britain, Prime Minister Tony Blair put its security forces on maximum alert. Following a security meeting Mr Blair said: "This is not a battle between the United States and terrorism, but between the free and democratic world and terrorism".
Security has been escalated in British airports. Civilian flights over central London have been banned following today's attacks.
Israel has closed its airspace for 24 hours to all incoming flights by foreign airlines, the Israeli Airports Authority said. The closure did not affect scheduled departures, the authority said in a statement, adding that security has also been stepped up at Ben Gurion international airport near Tel Aviv.
The US State Department has called on all diplomatic posts worldwide to take "necessary security precautions" in light of terrorist attacks on US targets. The official said the State Department had been evacuated "as a precaution" and the Deputy Secretary of State Richard Armitage "is in touch with Secretary of State (Colin) Powell in Lima."
In response to the statement, foreign embassies in Washington closed down or tightened security. The Mexican, Colombian, Canadian, Israeli, Spanish, British, French embassies either closed their doors or continued to function at a higher level of security.
Federal buildings in Washington, including those housing the US Congress, the State Department and the Central Intelligence Agency, were evacuated and closed, according to federal officials.
Most public transport in and out of New York has been suspended in the wake of attacks which led to the collapse of the World Trade Centre. Train travel from Boston to Washington has been suspended and New York's airports have been shut.
Airports closed in the New York area included John F Kennedy International, LaGuardia International Airport and Newark International.
All airports in the Washington area were also shut down in response to attacks on the World Trade Centre and the Pentagon. In Washington, Dulles International, Ronald Reagan Washington National and Baltimore/Washington International are completely shut down.
While the Los Angeles chief of police is saying that all is well in the city bomb squads have combed the evacuated city airport amid fears that the terrorism that struck earlier today could reach the west coast.
Both of the American Airlines flights as well as one of the United Airlines flights were bound for Los Angeles. The fourth flight used in today's attacks was en route for San Francisco.
The Federal Aviation Administration said it was diverting transatlantic flights headed for the United States to Canada after earlier grounding all flights in response to the attacks.
The US has closed all land borders in an effort to tighten security. All Canadian airports have now been closed because of the unfolding crisis.
New York Mayor Rudolph Giuliani urged New Yorkers to evacuate lower Manhattan after the two planes crashed at the twin towers of the World Trade Centre.
All US nuclear power plants, research reactors, nuclear fuel facilities and gaseous diffusion plants have been placed on the highest security alert. The US Nuclear Regulatory Commission said that the alert was "purely as a precaution".
US forces and their families based in Europe have also been placed on high alert.
