Indonesian officials today said they were worried about the possibility of accidents at over-stretched airports receiving aid for tsunami victims, and had opened another one to ease the congestion.

Flights have already begun to and from the island of Sabang, just north of tsunami-devastated Sumatra, said Budi Atmaji, chief of staff for Indonesia's relief operations.

He said officials were particularly worried about the airport in Aceh's provincial capital. Banda Aceh airport has just one landing strip and handled only three daily scheduled flights before the December 26 disaster. Now it is the hectic hub of one of the world's biggest-ever aid operations and is struggling to cope with about 200 daily airplane and helicopter flights.

"We are very worried about accidents," said Mr Atmaji.

A US Seahawk helicopter crashed in a rice paddy near Banda Aceh airport as it was trying to land yesterday, injuring two sailors. The US military said one fractured an ankle and another suffered a dislocated hip. It blamed the crash on a "possible mechanical failure" and said it was being investigated.

The shortage of airport capacity has also slowed aid deliveries - one day last week Banda Aceh's sole landing strip was closed for hours after a plane collided with a herd of cows.