China's C919 and Russia's MC-21 may be absent from the tarmac at the Paris Air Show, but their makers don't hide their ambition to nose into the biggest part of the civil aviation market -- single-aisle medium-haul aircraft -- which is dominated by Airbus and Boeing.
"For decades there were just two families of competing aircraft in the single-aisle segement, the A320 and the 737" built by Airbus and Boeing, said Stephane Albernhe, managing partner at Archery Consulting.
Both firms have been announcing business worth tens of billions of dollars for their mid-range bestsellers at the Paris Air Show, but they're unlikely to keep the market for themselves for long.
"Things are beginning to change because the duopoly is being attacked by the Bombardier's C Series, Comac's C919 and Irkut's MC-21.
While Bombardier's C Series entered into commercial service last year, both the C919 and MC-21 only just made their maiden test flights last month and are years away from entering into service.
The C919, which made its first test flight on May 5, built by state-owned aerospace manufacturer Commercial Aircraft Corporation of China (COMAC), represents nearly a decade of effort in a government-mandated drive to reduce the nation's dependence on Airbus and Boeing aircraft.
Capable of carrying 168 passengers over a distance of 5,500 kilometres (3,400 miles), the C919 already has 600 orders.
The MC-21 also represents an effort by Russia to end reliance on foreign aircraft. Since the collapse of the Soviet Union, Russian airlines have shifted to Airbus and Boeing aircraft which are cheaper to operate.
Manufactured by the state-owned Irkut, the aircraft made its first flight on May 28 over Siberia. Capable of carrying between 132 and 211 passengers up to 6,000 kilometres, there have been 175 orders for the MC-21 according to Irkut.
The MC-21's maiden flight comes six years after Russia's short-haul Sukhoi Superjet aircraft came into service in 2011. But they have since suffered serious technical issues that have forced the plane's grounding.
For Gilles Fournier, managing director of the Paris Air Show, "these planes are not yet mature enough to display" at the event. But, he added, "I think they will be in two years" at the next Paris Air Show.
"These new entrants have states which support them and they won't stop there," said Albernhe.
"They have started with single-aisle aircraft, but its a good wager that at least as far as the Chinese are concerned, the next model with be a long-haul aircraft."
In fact, Beijing and Moscow announced last month they intend to work together this time a long-distance aircraft, which has been baptised C-929 by the Chinese.
Capable of carrying 280 passengers on flights up to 12,000 kilometres, the C-929 would take on the latest long-haul jets offered by Airbus and Boeing -- the A350 and 787 Dreamliner.
The plane is to be developed by COMAC and Russia's United Aircraft Corporation (UAC). Chinese media have said development could cost between $13 billion and $20 billion.
- Biggest aviation market -
So far the Chinese are proceeding slowly to acquire know-how, and relying on their vast home market, to avoid a commercial failure.
According to estimates by Airbus and Boeing, the Chinese market will need around 6,000 new aircraft over the next few decades, making it worth a trillion dollars.
"It will take time before Russian and Chinese manufacturers acquire the technical and industrial maturity of Airbus and Boeing," cautioned Albernhe.
Until the C919 and MS-21 receive certification from US and European regulators the aircraft won't be able to truly compete for business internationally.
COMAC still hasn't received US certification for its ARJ-21 regional jet, which entered service with a Chinese airline in 2015 and remains limited to internal routes.
But the threat that China and Russia pose is taken seriously on both sides of the Atlantic.
"Never sell your competition short," said Randy Tinseth, vice president for marketing at Boeing's civil aviation unit.
"Ten years from now, 15 years from now, they will be the world largest aviation market," he said. "That's why they're investing in these products -- they have the biggest domestic market that puts them in a place no one else is."
The same message can be heard from Airbus.
"If you ask me 'are there any threats in the next five to ten years to Airbus or Boeing?' Probably not," said John Leahy, the chief operating officers for customers at Airbus' commercial aircraft unit.
But "in 20 years I think they will be one of the three big manufacturers of aircrafts," he added.
Business management consultancy AlixPartners also thinks it will take some time for the Chinese and Russians to really break into the market.
"Looking ahead, we don't expect the commercial aircraft duopoly of Airbus and Boeing to be heavily threatened in the near future, it will probably take another generation of new aircraft," said Eric Bernardini, who heads of aerospace and defence at AlixPartners
"However, an acquisition by the Chinese of Bombardier C Series would create a serious threat," he noted on the company's website.
The C Series has begun to make inroads in the global market, but Bombardier had to take on debt and was rescued by the Canadian provice of Quebec to finance building the aircraft, its first foray in the medium-range segement.