Originally Posted by
Fris B. Fairing
This was debated here some time ago and I recall that it is permissible to operate without one winglet but not both. I don't recall ever hearing a satisfactory explanation for this counter-intuitive requirement.
I flew on a All Nippon Airways 747-481D Haneda-Fukuoka (about a two-hour sector) which had no winglets. The story was that on short-haul they made no difference. I'm beginning to wonder whether they make any difference at all on long-haul now.