Airbus has failed to convince advertising monitors to castigate Boeing for publishing claims that its 747-8 achieves better fuel burn per seat than the A380.
Two specific Airbus complaints about the advertisement - which appeared in Flightglobal publication Flight International - have been dismissed by the UK's Advertising Standards Authority.
Boeing had claimed that the 747-8 was 8% more efficient than the A380 and had a 26% trip-cost advantage.
Airbus had objected to the efficiency claim on the grounds that Boeing was using a 467-seat configuration for the 747-8 against a 555-seat layout for the A380.
The European airframer argued that, to achieve the same comfort standard as the A380, the rival 747-8 would have to be fitted with only 405 seats - and that this would increase the per-seat fuel burn.
But the advertising authority points out that the Boeing claim referred simply to the basic fuel-burn figure, not the cabin comfort.
"Regardless of any difference in comfort standards, we considered it was reasonable to make the comparison based on standard seating layouts of the aircraft," it states in its adjudication.
It says the specialist target audience for the advertisement would also be familiar with the modelling and assumptions on which the claims were based.
Potential customers would "understand" that the "highly-customisable" nature of the aircraft would mean efficiency claims would be subject to "considerable variability", it adds, depending on a carrier's specified layout.
Boeing's trip-cost claim was based on an industry-standard cash aircraft-related operating cost methodology, applied over a 6,000nm (11,100km) route. A generic flight profile for the route indicated the 747-8 would burn around 121t of fuel compared with 157t for the A380.
This method laid down assumptions about the technical parameters of the aircraft being compared, and used an established process to ensure configurations were consistent - tailored to the customer's particular operation, including specific route profiles, if it supplied the necessary data.
Boeing also suggested that the methodology probably "understated" the true trip-cost advantage because it did not account for the A380's higher purchase price as well as other related finance considerations.
These performance characteristics, the adjudication rules, were only summarised by the advertisement.
"We also considered [customers] were unlikely to make a purchase decision without seeking a great deal more information on the potential advantages of the [aircraft], based on their own specific requirements," it adds. "For these reasons we concluded that the [advertisement] was unlikely to mislead."
Boeing says it welcomes the dismissal of the "unfounded complaints", and adds: "We are pleased that our advertisements underlining the advantages of buying Boeing products have been supported."