Runway length - is there more to it than aircraft size?
 

Just reading about LAS, where it talks of "Runway 07L/25R - Extended to be the second longest civilian runway in the country".

AFAIK, LAS handles very few widebodies, with 3 VS 747s each week being the main visitors. Philippine Airlines also operate an A340 via Vancouver. The vast majority of traffic there is along the lines of the B737's operated by Southwest, with AWA also operating a good mix of 319s and 757s.

Even when a 747 does visit, it is never likely to operate the kind of sector length which would push the runway to its limits, and as the city is mainly a destination, rather than a transfer hub, I don't see it being a major candidate for the A380 either (Ivanpah Valley is earmarked to take these sort of flights anyway).

A super-long runway wouldn't allow simultaneous take off / landings, (unlike, say a super long station platform which might handle two or three trains), so where is the big advantage in having such major runway extensions - is it something to do with the elevation / weather conditions, or is it just about ego (everything else there has to be the biggest, so why not the runway?).

Jet engines lose performance at high temperatures and elevations. LAS is 2170' high, and temps in the Nevada desert often top 40 C.

The other factors, other than runway length, could be the pavement strength of either the runways, taxiways or aprons, or the available size of parking aprons. LAS mainly deals in internal flights with smaller a/c such as 737, and bizjets.

Simple answer, longer runway = Heavier max landing/take off weight, but life is never that simple.

A 40 degree day at LAS gives a density altitude (ie air thickness) of around 6000ft. So in addition to the jets getting less air to suck each kt is about 10% faster than at sea level ISA, or the wing will make 10% less lift for same speed if you prefer. (would be glad to be corrected on figs). The 747 is only ever anywhere near performance limited at hot high airfields. We often get near ish limits on hot days in PHX (to LHR) so i would imagine VS often get limited at LAS on hot days as they have more seats than we do.

Also different aircraft need different runway lengths, although a 737 is lighter than a 757 the 757 will be airborne at a much slower speed than the 737.