<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>DuskStar</author><text>In addition to the other listed issues, it&amp;#x27;s above the altitude at which body temperature causes water to boil, commonly known as the Armstrong Limit. As you may imagine, this significantly complicates cabin depressurization incidents.</text><parent_chain><item><author>usaphp</author><text>What are the downsides of higher altitude flights?</text></item><item><author>asdfadsfgfdda</author><text>Less drag (lower air density) but also slower winds. Cruising at such a high altitude avoids the strongest jet stream winds.</text></item><item><author>dorfsmay</author><text>Why flying so high? Fuel economy?</text></item><item><author>skunkworker</author><text>If the claims about efficiency are correct, this aircraft has Prius-like levels of fuel efficiency. Incredible.&lt;p&gt;&amp;quot;The patent goes on to describe a notional aircraft that would cruise between 460 and 510 miles per hour at an altitude of up to 65,000 feet, yielding a fuel efficiency rate of between 30 and 42 miles per gallon. To put this in perspective, the Pilatus PC-12, a popular light, single-engine turboprop aircraft has a service ceiling of 30,000 feet, a cruising speed just under 330 miles per hour, and still burns, on average, 66 gallons of jet fuel per hour, for a fuel economy of roughly five miles to the gallon. Even going to a Learjet 70, which has similar speed performance to what&amp;#x27;s stated in the Celera patent documents, but still nowhere near as high a ceiling, we are talking about roughly three miles per gallon of gas at cruise.&amp;quot;</text></item></parent_chain></comment><story><title>The Celera 500L aircraft may fly soon</title><url>https://www.thedrive.com/the-war-zone/28409/the-mysterious-and-potentially-revolutionary-celera-500l-aircraft-may-fly-soon</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>bayesian_horse</author><text>Climbing that high takes time and fuel. Which you can recover somewhat on descent, but not totally, and under not-ideal circumstances like hiccups in the flight plan the plane even has to waste the potential energy.&lt;p&gt;I&amp;#x27;d say that altitude is the reason for the focus on long distance.</text><parent_chain><item><author>usaphp</author><text>What are the downsides of higher altitude flights?</text></item><item><author>asdfadsfgfdda</author><text>Less drag (lower air density) but also slower winds. Cruising at such a high altitude avoids the strongest jet stream winds.</text></item><item><author>dorfsmay</author><text>Why flying so high? Fuel economy?</text></item><item><author>skunkworker</author><text>If the claims about efficiency are correct, this aircraft has Prius-like levels of fuel efficiency. Incredible.&lt;p&gt;&amp;quot;The patent goes on to describe a notional aircraft that would cruise between 460 and 510 miles per hour at an altitude of up to 65,000 feet, yielding a fuel efficiency rate of between 30 and 42 miles per gallon. To put this in perspective, the Pilatus PC-12, a popular light, single-engine turboprop aircraft has a service ceiling of 30,000 feet, a cruising speed just under 330 miles per hour, and still burns, on average, 66 gallons of jet fuel per hour, for a fuel economy of roughly five miles to the gallon. Even going to a Learjet 70, which has similar speed performance to what&amp;#x27;s stated in the Celera patent documents, but still nowhere near as high a ceiling, we are talking about roughly three miles per gallon of gas at cruise.&amp;quot;</text></item></parent_chain></comment><story><title>The Celera 500L aircraft may fly soon</title><url>https://www.thedrive.com/the-war-zone/28409/the-mysterious-and-potentially-revolutionary-celera-500l-aircraft-may-fly-soon</url></story>