Originally Posted by
jrl767
iirc there was a similar question on the Alaska board a couple months ago; someone replied that the 738/739 fleet is limited to 25000 ft if one A/C pack is inop
Likely winner, almost all modern passenger jets are limited to about FL250 with an A/C pack out…and FL240 is correct altitude for direction of flight on the route taken (N and E Odd, S and W Even). It’s also often the lowest altitude for “High Altitude” ATC Sectors, and thus keeps frequency changes down due to larger sectors compared to the Intermediate and Low Sectors.