Qantas says it is embarrassed by two security breaches at its Brisbane Airport terminal in one week.
The top floor of the Brisbane domestic terminal was evacuated last night after a number of people walked through a Qantas screening area without being checked.
Passengers who had already boarded planes were forced to disembark and return to the security screening areas.
Flights were delayed by up to two hours.
It is the second such incident at the Qantas terminal in a week.
Qantas spokesman Geoff Askew says the airline is assessing what went wrong.
He says plans are in place to redesign check points.
"This was an error there's no mistake about that we erred and we will take remedial action," Mr Askew said.
The Brisbane Airport Corporation's Rebecca McConachie says they are working with Qantas to improve its security.
"We'll be working closely with them to make sure that these issues are addressed," she said.
Office of Transport Safety is investigating the security breaches and spokesman Paul Retter says a communication breakdown was to blame.
Mr Retter says the incident is unacceptable and the Qantas and security contractor ISS will have to work hard to fix the problem.
"ISS has been undergoing a fair amount of work with their staff to improve their training and I'd have to say that our assessment of the work that ISS is doing to improve its situation at Brisbane Airport has been pleasing," he said.
"Obviously the last two incidents reveal a number of weaknesses that we'll need to address.
The Transport Workers Union (TWU) is calling for an overhaul of airport security systems.
Scott Connolly from the TWU says a single government agency should be responsible for enforcing airport security standards.
"The question comes down to enforcability and the department or the government agency drilling these enforcement mechanisms down and making the contractors or ultimately BAC (Brisbane Airport Corporation) or Qantas responsible for ensuring we have uniform standards," he said.