Bombardier has delayed the CSeries first flight up to four more weeks to install another round of software upgrades.
The update comes after Bombardier executives said last week that they still expected first flight of the FTV1 test aircraft to occur before the end of June.
It also extends the six-month delay Bombardier announced last November for the CSeries first flight, which the aircraft maker blamed on late suppliers.
But Bombardier still plans to deliver the first CS100 version of the CSeries to launch operator Malmo Aviation by July 2014.
The first flight may now be timed around the fifth anniversary of the CSeries launch event at Farnborough 2008.
"Only five years after launching the CSeries airliner, we're approaching our maiden flight - a historic moment for Bombardier and a game-changing moment for the industry," says Mike Arcamone, president of Bombardier Commercial Aircraft.
Bombardier will spend the next few weeks completing final preparations.
The FTV1 airframe must complete a battery of power tests of the onboard systems. The aircraft will then move to the flight line for a series of low- and high-speed taxi tests, including a rejected take-off scenario.
All suppliers have submitted safety of flight statements, Bombardier says.
The flight test centre, meanwhile, has applied for a flight test permit for FTV1 to Transport Canada. The regulator must approve the permit to allow Bombardier to fly the CSeries.
The first flight will help Bombardier regain some momentum for the CSeries programme. The new single-aisle failed to attract any new firm orders during the Paris air show, and the backlog remains stuck at 179.
For several months, Bombardier officials have said they anticipate new firm orders after completing the first flight milestone and that they are confident they will sign 300 firm orders before the type enters service next year.
The CSeries is aimed at the niche of the single-aisle sector between 110 and 130 seats. It is designed with several new technologies for Bombardier and this segment of the narrowbody market, including a composite wing, fly-by-wire flight controls and the Pratt & Whitney PurePower PW1500G geared turbofan engine.