Whitehatter
Couple of pointless replies there seeing as the 747 and 737 both have winglets
Do Boeing actually make the winglets for the B737?? Or are they made by another company in Renton? You might also find that this other company was formed by ex-Boeing engineers who were disappointed that Boeing wouldnt make winglets. So why do you think that Boeing wouldnt listen to its own engineers?
As for the B744, its 1980's technology, they couldnt increase the span, so it had to have winglets
Mutt