[ABC News]
Flights around the country are being delayed or cancelled tonight because of a shortage of air traffic controllers at Sydney airport.
Some planes are circling for at least 45 minutes before landing, while many passengers on the ground are being forced to spend an extra night in Sydney.
Air Services Australia (ASA) says three employees called in before their shifts this afternoon to say that they could not come to work.
A spokeswoman says it is not related to any industrial matters but is unable to say whether it is because they are sick or have had to take the day off for personal reasons.
She says replacements were unavailable.
A spokeswoman for Virgin Blue says there will be cancellations and delays, with some people having to be accommodated overnight.
She says planes are circling for at least 45 minutes before landing in Sydney.
Qantas says its flights have been delayed for up to an hour.
ASA says flights should be back to normal tomorrow.
Sydney airport officials have refused to comment, saying it is a problem for Air Services Australia.