US airspace re-opens

US Transport Secretary Norman Mineta has re-opened US airspace to commercial flights.

Nearly all commercial aircraft in America had been grounded since the devastating terrorist attacks on the US on Tuesday.

But Mr Mineta said airspace had been reopened at 1100 EDT (5pm Irish time), with investigations ongoing to decide which flights will be permitted to fly through it.

"We will re-open airports and resume flights on a case-by-case basis, only after they implement our more stringent levels of security," said Mr Mineta, adding that the decision was good news for travellers, the economy and the for the restoration of the freedom of America's mobility.

Aer Lingus is still grounded for trans-atlantic flights to the US. They are waiting to hear from the American authorities for the date when they can resume normal service to America.

The terrorist attacks have caused chaos at airports around the world, as well as hitting at the heart of the US financial world.

The return to normal air services is expected to be very gradual.

orthwest: Flights at 2400 GMT ( 5am Irish time)

Delta: flights to resume from 1600 GMT (9pm Irish time)

New security measures

All knives banned

Strict screening measures

Vehicles more carefully monitored

No scissors

No kerbside check-ins

Boarding area off-limit to everyone but passengers

Armed plain-clothes guards on some flights

Each case will be reviewed on an individual basis, and airports will only be re-opened when they have proved that stringent new security checks are being met.

And US authorities plan to draft in Delta Force commandos to help protect civilian planes.

The US Government allowed limited flights on Wednesday so that planes diverted during the attacks could reach their original destination.

"Safety is always of paramount importance, and in these extraordinary times we intend to be vigilant as we remain committed to resuming commercial flights as soon as possible," said Mr Mineta.

The International Air Transport Association has estimated that this week's flight cancellations will cause the air industry $10bn.

Slow start for trans-atlantic flights

The resumption of flights will start the flow of a limited number of people out of airports already filled to bursting with stranded passengers.

It has been confirmed that an Alitalia Boeing 747 took off for the US at 1610 GMT.

In the UK, flight restrictions over London were lifted and London City Airport will open from midnight.

But British Airways said that three trans-atlantic flights scheduled to depart to America from Heathrow airport on Thursday night were now unlikely to fly.

Delta, Northwest and United Airlines said they tentatively planned to resume flights from Germany on Friday.

American Airlines says it will complete 153 of its flights that were diverted on Tuesday, while both United Airlines and Delta will begin a limited service from 1600 GMT.

Southwest airlines will not resume flights on Thursday, while Northwest expects to fly its first plane at midnight.

Lack of space

Industry specialists said restoring world air travel to normal is likely to be a prolonged affair, because of the need for extremely tight security measures, the lack of space for airplanes on the ground, and a necessary reshuffling of the location of planes that had been diverted.

Under normal circumstances, a large proportion of the world's planes are in the air rather than on the ground.

Space at airports is scarce, so landing planes within a narrow timeframe presents huge logistical difficulties.

An estimated 4,000 commercial aircraft - almost one third of the world's fleet - were grounded in the US shortly after the attacks on the World Trade Center and the Pentagon.

After what has been called "the blackest day aviation has ever had", the airline industry is also facing severe financial consequences.