The only mod I'm aware of is the high altitude landing switch.... which all of our 757s have. It reprograms the system logic to reset the cabin altitude/aural warnings to 14,650ft instead of the usual 10,000ft (obviously due to La Paz field elevation.) So any/all of our 757s can do the flight.

The only flights we have in there are from MIA. It is a MIA-La Paz all nighter, followed by a tag leg to VVI (Santa Cruz) where they lay over. Flown by three pilots. They all have to be on O2 on the approach/landing, and the FO usually takes a bottle (of O2, that is...) with him/her on the walkaround. Interesting stuff.

I think LPB is the only airport we serve that requires exclusively a 757. The 738 could probably do it, but it would need that high-alt landing switch.