Question: If winglets significantly help efficiency, why do some airlines still orders winglet-less aircraft?
The first is cost of purchase, the 737NG winglets cost roughly 1 million dollars to retrofit. It could cost an airline 50 million dollars (more than a single fully loaded 737NG) to retrofit a modest fleet. Granted airlines with large fleets have the most to gain, but it isn't as if winglet-less aircraft are un
profitable. Remember that it takes a 737NG roughly 5 years (depending on airline) to recoup the cost of purchase.
The second is gate space. 737NG opperators FL
both have this problem, some of their airports can fit winglet 737s and others can't. It is a bigger hassle to rework an airport terminal than it is to fly with a little more fuel burn....
The third is if the airline can even benefit from the winglets. Most
can extract some benefit, but it varies from airline to airline
PPVRA: It is my understanding that the reduced drag only realises a fuel savings over longer routes, so the expense of the winglets (and approvals, etc?) is not always worth it for airlines with mostly shorter hauls
Sometimes yes sometimes no. WN
states they will benefit from the winglet package on any flight over 48 minutes, but other airlines require up to an hour or more.