The two rival machines that went head to head in the skies above Farnborough highlighted the headache that airlines face when planning their new fleets: that delivery schedules tend to come with a health warning attached.

The Qatar Airways Boeing 787, which made its debut at the show, was originally due to touch down in Doha more than two years ago. Remarkably, that delay almost fades into insignificance compared with that of the Malaysia Airlines Airbus A380, which was also on show. For when MAS originally ordered its fleet of the double-deckers, its first aircraft was due to arrive more than five years ago.

And had Airbus stuck to the original development schedule for its new A350 XWB when it was unveiled at Farnborough in 2006, the first aircraft for Qatar Airways could well have been in the flying display, given that deliveries were due to begin in mid-2012.

To be fair to Airbus, by the time the XWB was launched at the end of 2006, the delivery date had slipped to 2013. But even that revised target is now long gone, as assembly is only now beginning of the first flying prototype.

T'was ever thus, some might say. At a recent event to mark the 50th anniversary of the legendary VC10, a senior aerodynamicist recounted Vickers' despair when discovering that drag was far higher than the windtunnel had indicated - to the tune of a two digit percentage margin. A lot of extra flight-testing, aided by some very rudimentary tools and analysis, tackled the problem. But the development programme ran into almost two years.

Such events were not unusual back in those pioneering days of jet airliner design. But surely stumbling over such "unknown unknowns" should have been relegated to the history books by now?

It looked like Airbus and Boeing had cracked it in the 1980s and 1990s, when all-new airliners such as the A320 and 777 sailed through flight-testing and hit their delivery marks.

But schedule delays returned with a vengeance in the 21st century, when the A380 ran into its now infamous wiring problems. This new low point for the industry didn't last long, though, as Boeing went one better with production headaches that blighted the Dreamliner.

A380 customers are still suffering, of course. As one customer said, the superjumbo has run into "disappointing" wing crack problems that will threaten more delays or downtime.

So it was no surprise that the revised development plan for Airbus's next big programme, the A350, came under scrutiny at Farnborough. The current schedule is for the first A350-900 to fly around the middle of next year and enter service in mid-2014. Airbus chief executive Fabrice Brégier says that it is "too early" to determine whether the schedule will change again as assembly progresses.

"It's easy on a programme like this to bet that we will be late. When you refer to the past programmes like the A380 and 787, these were delayed by about three years and we have no intention to repeat these mistakes," he says, but cautions that if any issues arise, he would "never exclude a slight hesitation".

Several of the other new airliner designs currently in development - such as the Mitsubishi MRJ, Russia's MS-21 and China's ARJ21 - are already facing "hesitations". And while Bombardier remains committed to its CSeries timetable as the first flight target approaches, it admits the schedule will be challenging.

So building "buffers" into delivery timetable planning is now de rigeur for most airliner launch customers. But perhaps this may not be necessary for 737 Max launch customer Southwest.

Programme manager Beverly Wyse tells Flightglobal that she is committed to delivering the first 737-8 in the fourth quarter of 2017, but "we're looking to see if we can target that earlier". Boeing's sentiment is admirable, but it would appear to have the weight of modern history stacked against it.

The Flightglobal team were out in force at Farnborough to cover the air show from every angle. For all the news, images, videos, dailies, blogs and i-mags, and to see Boeing's return to air-display flying after almost three decades (right), visit:

Source: Airline Business