Qantas is being investigated by Britain's advertising watchdog for claiming in a series of advertisements that it is the "world's most experienced" airline.
The Advertising Standards Authority (ASA) has received eight complaints about a series of print and television ads for the Australian airline which ran in Britain earlier this year.
An ASA spokesman said Qantas was cooperating with the investigation and had defended the claims made in its ads.
"We have had complaints about the TV and poster advertisements and the use of the line that Qantas is the world's most experienced airline," the spokesman said.
"Viewers have challenged whether it is misleading because they believe there are other airlines that were established before Qantas.
"It's an ongoing investigation as to whether there's a problem under our code."
Comment was being sought from Qantas.
The ASA's investigation is expected to be completed within the next few weeks.
However, the ASA is not a statutory authority so is unable to do much more than give Qantas a public slap on the wrist if it finds the airline's claims are misleading.
According to Qantas' website, the airline was formally established in Brisbane on November 16, 1920, and by 1921 its fleet consisted of two war-surplus biplanes.
However, other small airline services were also operating in the United States around the same time.
The investigation comes after Qantas was last year dragged into the ASA's probe into Tourism Australia's controversial "Where the bloody hell are you?" advertising campaign.
Qantas airfares were promoted in the ads, which were condemned by the ASA for using a swear word and ultimately banned after the watchdog received 32 complaints about the promotion.
The airline has been dogged by a spate of controversies involving its aircraft in recent months.
The Civil Aviation Safety Authority last month launched its own investigation into Qantas' safety and maintenance operations after three mid-air emergencies on its jets in less than 10 days.
