To gauge the impact of Bombardier's decision on 26 June to wait up to another full month to fly the first CSeries test aircraft, it's useful to remember the interests of potential customers.
Qatar Airways chief executive Akbar Al Baker started negotiating a CSeries deal with Bombardier almost five years ago, but still refuses to write a cheque until he sees the aircraft fly.
"We want to see what are the problems, what are the outstanding performance that was promised during the time that we negotiated with them," Al Baker said in a Paris air show interview. "Once this is resolved and the aircraft is well in its flight test, we will then look into it."
Bombardier acknowledges that Al Baker is not alone. The CSeries programme makes big promises, including a 15% cash operating cost advantage over Airbus and Boeing rivals. Some potential buyers want to see how the CSeries - which introduces such advances for a narrowbody airframe as a composite wing, fly-by-wire flight controls and a geared turbofan engine - performs before they believe.
For more than a year, Bombardier has answered questions about the slow pace of CSeries sales by pointing to the first flight milestone as a critical event for some potential customers.
"By September, we'll no longer be selling a brochure airplane," said Chet Fuller, senior vice-president commercial, at the beginning of the show. "We'll be selling hard data."
Bombardier executives also have all but guaranteed that the CSeries will enter service in the third quarter of 2014 with at least 300 firm orders in the backlog - a 69% jump from the current level of 177.
All of that still depends on the timing of first flight. So far, Bombardier's existing customers have been patient. Only three aircraft orders were cancelled during the initial, six-month delay period announced last November, a setback that Bombardier blamed on lagging suppliers.
On 26 June - and less than a week after top executives asserted the contrary at the Paris air show - Bombardier acknowledged the first CSeries test vehicle would not be available to fly until July, representing a new delay of up to a month.
The signs of another delay were apparent even as Bombardier executives said otherwise. There had been no sightings of the FTV1 flight test vehicle performing a battery of required low- and high-speed taxi tests, including the critical rejected take-off test, on the runway outside Bombardier's CSeries final assembly centre in Mirabel, Canada.
Bombardier now says the runway tests are delayed to complete a final round of software upgrades to improve "system maturity and functionality", based on requests by the CSeries flight-test team. Meanwhile, suppliers have submitted all of the required safety of flight certifications for systems, and Bombardier has applied to Transport Canada for a permit to fly the first CSeries test aircraft.
"Departmental officials are in the process of reviewing the application to determine that all criteria are met," Transport Canada says.
In another major development, Bombardier completed all ground vibration testing on the CSeries on 14 June, a prerequisite to moving forward on first flight of FTV1.
By contrast, Boeing completed ground vibration testing on a 787 airframe in early May 2009, or nearly two months before a then-scheduled first flight. Only a month later, however, Boeing announced finding structural weaknesses where the wing meets the fuselage, which delayed the 787's first flight for another six months.
By the standard set by the 787 programme, the CSeries is progressing well so far on its development schedule despite a more than six month delay. In addition to the structural problem, the 787 schedule also was disrupted by breakdowns throughout Boeing's production system.
Bombardier has only reported a hiccup with rear fuselage supplier Shenyang last June, but said in an update in March that the problem was resolved. Pratt & Whitney certificated the PurePower PW1500G geared turbofan about seven months later than normally expected in February, but the engine is now available for flight test. The Parker Aerospace-supplied fly-by-wire system has been a focus of questions outside the programme, but Bombardier so far has reported no concerns about its performance.
Bombardier credits the lack of drama over the CSeries technologies to an upfront investment in a vast testing and simulation complex in Mirabel. Workers even built a full-scale wooden mock-up of the CS100 flight test vehicle in the Mirabel factory. Potential customers such as Al Baker will continue scrutinising how the technology performs in flight test, but so far the CSeries programme has avoided raising any alarms.
The biggest questions swirling around the CSeries programme still concern the business model and sales strategy, and the latest delay for first flight only extends such anxiety for at least another month.
Bombardier has faced questions about its negotiating style on CSeries customers almost since the beginning. In 2011, the influential chief executive of Air Lease, Steven Udvar-Hazy, publicly chafed about the premium he felt Bombardier placed on the CSeries price tag. Bombardier, for its part, does not discuss pricing strategy in detail, but overall says the company wants to be compensated fairly for the value the CSeries should deliver to customers.
But the doubts still linger, and arose again among another major lessor at the Paris air show in late June. International Lease Finance Corporation (ILFC) chief executive Henri Courpron said the lack of customers for the CSeries - and the large portfolio of existing E-Jet operators - drove the lessor's decision to sign a letter of intent for up to 100 Embraer E-190 and E-195 E2s.
"There is no customer base on which you can build," he says. "I hope for them that they will."
Fuller responds: "For ILFC it's all about the customer base. We've said in the beginning it's about getting the customer base and expanding the geographic spread [of Bombardier operators]."
Fuller's case for the CSeries was slightly undermined, however, by a lack of new orders announced at the Paris air show. Bombardier instead watched as Embraer launched the E-Jet E2 family with 364 combined orders and commitments, approaching in one week the cumulative, five-year sales record of the CSeries with 388 orders and commitments.
The E2 family includes three variants, including two - the E-190 and E-195 ¬- that compete with the CS100, albeit with a four-abreast fuselage instead of five-abreast and with less range. The launch was significant, however, because it opened a two-front sales war on the CSeries, with Embraer challenging the CS100 and Airbus and Boeing fighting the CS300.
Unlike the CSeries family, the A319neo and the 737 Max 7 are not optimised for the 125-150 seat segment they occupy. Instead, each is a shorter version of a fuselage and wing sized to be most efficient in the single-aisle market segment above 150 seats. That gives the CSeries a natural advantage on empty weight, which usually corresponds to a lower overall trip cost.
On the other hand, Bombardier has never amassed the marketing and financial power of the Airbus-Boeing duopoly. The CSeries was launched two years before Airbus decided to shelve plans to launch an all-new narrowbody, and simply re-engine its existing family of aircraft. Boeing decided to follow suit eight months later after the A320neo had already staked an orders lead of some 800 aircraft.
Bombardier, however, still exudes an easy confidence about the CSeries prospects despite the rising competitive pressures.
Fuller calls Embraer's E2 "uncompetitive" with the CSeries because it is a smaller aircraft. "Improving the engine and improving the wing a little bit will make a marginal aircraft a little bit less marginal," he says.
Bombardier's history in the aerospace industry may help explain its confidence. This is the same manufacturer that launched a 50-seat regional jet called the CRJ100 almost 25 years ago when no such market existed. Yet, the aircraft sparked the regional jet revolution in air transport during the 1990s and led four major derivatives.
Company officials recall similar pressures and initial doubts when the CL-600 Challenger was launched in the early 1980s and the Q400 turboprop was unveiled in the late-1990s. Each time, the programmes managed to overcome the sceptics and any technical issues and be successful in their market niche.
The CSeries reflects Bombardier's entrepreneurial history. It offers, for example, a best-in-class suite of technologies. The composite wing, fly-by-wire flight controls, aluminium-lithium fuselage panels and geared turbofan engines are all new to the single-aisle sector. The CRJ100 was barely noticed by the market until the fleet owned by Delta Air Lines' now-defunct regional subsidiary Comair started making a noticeable difference on the parent company's balance sheet in 1992. In due course, other airlines quickly lined up to buy the aircraft. The CSeries performance, if it matches Bombardier's promises on paper, may have the potential to general similar customer interest after it enters service.
On the other hand, Bombardier has never faced competitors with the critical mass and leverage of Airbus and Boeing, nor has it faced a battle on two fronts in the commercial aviation market with a single product family. The company's attitude, however, is clear enough.
"Never give up, never surrender," says Fuller.
Bombardier still plans to deliver the first CS100 version of the CSeries to launch operator Malmo Aviation by the third quarter of 2014.
The first flight may now be timed around the fifth anniversary of the CSeries launch event on 13 July at the Farnborough air show in 2008.
"Only five years after launching the CSeries airliner," says Mike Arcamone, president of Bombardier Commercial Aircraft, "we're approaching our maiden flight - a historic moment for Bombardier and a game-changing moment for the industry."
Additional reporting by Edward Russell