Just because you can't gain efficiency by changing the speed of the plane, with no other changes allowed, doesn't mean you have no options :
1) reduce weight (fuselage, engine, wings, have the passengers diet first, ...)
2) increase engine fuel efficiency, displace more air for fewer hydrocarbons
3) (in the article) reduce drag on surfaces that don't generate lift
4) lower cross section (a longer, thinner tube), of course, still needs structural soundness
The lower cross section would have the additional advantage that it would make the plane fly faster.
So in a way, the article is "wrong". You can make a faster plane, assuming you can solve all the issues that the obvious modifications bring : longer, thinner and lighter fuselage and wings, combined with similar efficiency engines (of course they'd have to have that similar efficiency at higher speeds).
Another way would be to fly (much) higher. But then the cost of climbing high would start to offset the gains from flying faster.
Comments
Just because you can't gain efficiency by changing the speed of the plane, with no other changes allowed, doesn't mean you have no options :
1) reduce weight (fuselage, engine, wings, have the passengers diet first, ...) 2) increase engine fuel efficiency, displace more air for fewer hydrocarbons 3) (in the article) reduce drag on surfaces that don't generate lift 4) lower cross section (a longer, thinner tube), of course, still needs structural soundness
The lower cross section would have the additional advantage that it would make the plane fly faster.
So in a way, the article is "wrong". You can make a faster plane, assuming you can solve all the issues that the obvious modifications bring : longer, thinner and lighter fuselage and wings, combined with similar efficiency engines (of course they'd have to have that similar efficiency at higher speeds).
Another way would be to fly (much) higher. But then the cost of climbing high would start to offset the gains from flying faster.