An Australian teenager looks set to spend his third night in a cell ... after joking about having a bomb on an Air New Zealand flight to Sydney

Meke Fifita has admitted making the comment on Wednesday night.

He's been convicted and sentenced, but is still stuck in a cell - unable to enter the country and unable to go back home.

Authorities are trying to deport the 19-year-old back to Australia, but Air New Zealand wants a security assessment carried out first.

In a statement, the national airline says it's standard procedure in cases of this nature for its Security Team to carry out such an assessment, before deciding whether the customer can continue to travel.

Fifita's lawyer is hoping her client can get on a plane by Sunday.