SYDNEY (Reuters) - Qantas Airways Ltd QAN.AX plans to have more experienced pilots on board the world's longest non-stop flights than on its current long-haul flights for the first 18 months as it evaluates fatigue, said sources with knowledge of the matter.

FILE PHOTO: Qantas aircraft are seen on the tarmac at Melbourne International Airport in Melbourne, Australia, November 6, 2018. REUTERS/Phil Noble

The airline said last week it could buy up to 12 Airbus SE AIR.PA A350 planes for the commercial flights of up to 21 hours that includes the Sydney-London route, but the deal depends on pilots voting to approve a pay agreement in March.

“To be clear, we have not yet placed an order for this aircraft because we still have a gap to close in the business case,” Qantas Chief Pilot Dick Tobiano said in an internal memo to pilots seen by Reuters.

Qantas said Australia’s aviation regulator had provisionally advised it saw no regulatory obstacles to the flights, which could extend pilot duty times to as long as 23 hours to account for potential delays.

The airline has conducted crew fatigue studies on London-Sydney and New York-Sydney test flights.

On its current long-haul flights, Qantas has a crew of one captain, one first officer and two second officers, the latter of which can only fly at cruising altitudes and cannot perform takeoffs or landings.

Rival Singapore Airlines Ltd SIAL.SI uses two captains and two first officers on its near-19 hours flights from Singapore to New York.

Qantas has offered to crew non-stop flights to London and New York with one captain, two first officers and one second officer for the first 18 months so it can evaluate fatigue-related issues, according to its pilot union newsletter, two pilots and a company source familiar with the matter who were not authorized to speak with media. Qantas declined to comment.

Qantas has proposed the pilots on its A330 fleet, which fly mostly cross-country and Asian flights, also fly the ultra-long haul missions on the A350, since they can be licensed on both models.

A Civil Aviation Safety Authority spokesman said it had yet to receive a formal application for the flights that would allow it to make specific requests on matters such as experience levels but the airline’s overall ultra-long haul safety framework provided a “satisfactory and detailed analysis of the identified risks”.

Adam Susz, a 737 captain and union negotiator for the Australian and International Pilots Association, said Qantas had tabled a draft proposal that had been deemed unacceptable by the union committee, in part because it introduced a lower pay scale for new second officers. But he said talks would resume in the new year.

“I am pretty confident that we will get agreement in the end,” Susz told Reuters on Monday. “I don’t think the issues are insurmountable but there are a couple of elements to the Qantas proposal that we find extremely unpalatable and we will avoid those the best we can.”