The Australian and International Pilots Association is warning against single-pilot flights, arguing they compromise safety.
The UN body that sets aviation standards has been asked by more than 40 nations to help make single-pilot flights a reality by as early as 2027.
AIPA President and Qantas A330 Training Captain Tony Lucas warned a single pilot could become overwhelmed in an emergency.
"The people going down this route aren't the people who fly jets every day. When things go awry, they go awry fairly quickly," he said.
"The best safety mechanism we have is two well-trained, well-rested pilots flying the aircraft."
Captain Lucas said single-pilot flying would also limit training and knowledge-transfer opportunities and negatively impact pilot fatigue and mental health.
Captain Lucas backed legendary Qantas captain Kevin Sullivan who warned against single pilot flights on Thursday.
"The authorities would benefit from listening to well-respected pilots like Captain Sullivan, who know first hand how multiple pilots working together can save lives," he said.
