Air travel chaos: Struggling airlines want blanket ban lifted

Have aviation authorities over-reacted?

Some in the travel industry claim the decision is over-cautious and has been made without proper assessment of the actual risk. Pilots, former pilots and airlines have suggested they would be willing to fly. But Tessa Jowell, of the government's crisis response committee Cobra, said the "over-riding consideration" needed to be the safety of passengers.

What is the main argument for relaxing the restrictions?

The ban on commercial flights is harming an industry already under financial strain. In addition, thousands of people have been stranded, affecting businesses and schools.

So why has the eruption caused more chaos than past incidents of volcanic activity?

In most volcanos, this initial stage of ash plumes is quickly followed by lava flows. But Mount Eyjafjallajkull is situated below a glacial ice cap, meaning magma is cooled quickly, causing plumes of ash and grit that could continue for months.

In addition, the relative weakness of the eruption means that the ash cloud is at a lower level. A stronger eruption would have seen the debris pushed above flight altitude.

What have airlines done to try and persuade authorities to relax the restrictions?

A number of European carriers have carried out test flights. After flying a Boeing 747 for nearly three hours on Sunday, BA said: "The conditions were perfect and the aircraft encountered no difficulties."

Dutch carrier KLM revealed it had flown a plane through the cloud of volcanic ash without suffering any damage.

Restrictions are being relaxed in the UK – is the worst over?

Having imposed the ban, it would be difficult to reverse it if there is no guaranteed improvement. Such a move would imply that there had been an initial over-reaction. Moreover, a major incident would leave authorities open to accusations that they had bowed to industry pressure.