Cruise climb
Good one. But as a non pilot old time flyer, just how high can today's jets sustain cruise in commercial conditions. I remember the early Comet IVs out of Melbourne seemed to fly right on 40,000 feet most of the time perhaps because there was nothing else up there, and it did see 43,000 feet showing on the Qantas 747SPs on the Pacific flights, and more recently I saw 40,000 feet on an Emirates A345.
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I seem to recall when sitting either the UK CPL or maybe ATPL Flight Planning paper during the early 1960's that cruise-climb based on both the Comet and Britannia performance models was something that, at least in my case, took a certain amount of practice to get up to speed on. As with take-off performance, there were a few fold-out graphs and tables to be tackled. Some questions required working backwards from supplied weight and fuel figures at final cruise Flight level or similar. ( However we had smart Navigators to fly with, and who were specially good at sums. )
My point is that when the skys were generally less cluttered a continuous gradual climb from initial cruise altitude to final cruise altitude was allowed.
Both Turbo-props and pure jet aircraft had their particular periods of advantage in flight levels achievable into less busy skies, as of course Concorde did later on. I remember us still being able to cruise climb Britannias on North Atlantic and sub-Polar routes around 1966, or thereabouts. Pressure pattern navigation ( single heading/Zn formula to those who remember....... but don't ask me to explain ) was still in the Nav manual, but the only time I tried that was when our Chief Navigator cleared it with Shanwick and Gander in order to demonstrate to us that it worked.
I don't think our passengers were necessarily aware that we were creeping up in altitude for hours on end. I'm fairly sure Australian ATC let us do it at higher levels in the 707 days if there was nothing else around.
I suppose now there aren't that many available spaces in the sky for cruise climb, but I think we did it once before this person returned to shorthaul around 1999. Northern Europe to Japan ( 747-400 ) on a day when there was nothing between Northern Greenland and the Aleutians except us....well it passed the time.........
Maybe when oil hits $??? a barrel, cruise climb may once again be possible. Could save a bit of the precious fluid, as long as people can still afford to drive to the airport...........