Theme 1 – Practical aviation constraints dominate any “optimal” routing
Commenters repeatedly stress that real‑world flight planning must respect ATC instructions, waypoint structures, airspace classes, ETOPS, NOTAMs, crew‑duty limits, and other regulatory/human factors.
- “When flying on oceanic routes and even on land, you have to intercept certain waypoints and vectored into/around airspaces.” – subhro
- “And never have to intercept certain waypoints when entering different classes of controlled airspace on the correct general heading to line up for a documented runway approach.” – walrus01
- “The commercial solutions exist because they consider not only the winds and fuel costs … but also known previously cleared ATC routings, altitude restrictions … expected delays … pilot and cabin crew pay, crew duty time limits … contracted lease, finance, insurance, and maintenance rates … airport arrival curfew times.” – buildsjets
- “It will never work because you have too many human processes in the loop.” – contingencies
Theme 2 – Fuel and time savings are attractive but must be weighed against other operational costs
Several posts highlight the potential gains (e.g., 45 min faster, 25 % less fuel) while noting that crew expenses, ETOPS compliance, and curfews can erode or even outweigh those benefits.
- “One point at 45 min faster and 25 % less fuel is of course huge, but how does it map out over a year of routing?” – ggm
- “The fuel consumption feels like the bigger problem since contrails last for hours vs CO₂ that lasts damn near forever.” – hackernud3s (illustrates focus on fuel savings)
- “Pilot and cabin crew pay, crew duty time limits (your more fuel‑efficient route may take longer and require an entire second crew)… contracted lease, finance, insurance, and maintenance rates … are also frequently paid by the hour.” – buildsjets
Theme 3 – Environmental impact: contrails vs. CO₂ is a debated focal point
A side conversation examines the climate relevance of contrails, with some arguing they rival historic CO₂ emissions and others asserting CO₂ remains the harder problem.
- “Recent estimates show that contrails cause about the same amount of warming each year as all the CO₂ emitted by all flights from 1940 to 2018.” – ZeroGravitas
- “If we're measuring in terms of difficulty, CO₂ is a much bigger problem than contrails.” – hackernud3s
- “Fun fact, contrails contribute to global warming, but only at night. During the day they have a cooling effect …” – margalabargala
- “[The source] acknowledges the difference between day and night but claims that the sum of the effects still results in net warming during the day.” – tgsovlerkhgsel