Ask the Pilot: All about altitude
Captain Mike Bowers is chief pilot at our Newark Liberty International Airport (EWR) hub. This United Hub series is based on our column in Hemispheres magazine, in which Mike answers questions from our customers. This month's Q&A is all about altitude.
Q. Are winds more consistent at flying altitude? I.e., on the ground there are days when it's calm — are there always winds at flying altitude?
A. Generally speaking there are almost always winds at altitude, but the location and intensity vary much as they do on the surface. On average, we see winds in the range of 80-100 mph. I have seen winds at altitude above 200 mph and I have also seen calm winds. The strongest winds are closest to the core of the jet stream which normally comes down from the West Coast dipping lower across the central U.S. and then curving northeasterly near the East Coast. The location varies but that is the general pattern. In the Caribbean it is not uncommon to have calm winds at altitude. Each region has its own wind patterns.
Q. On a recent flight the pilot said that we'd start the flight at 35k feet and "after we burn some fuel we'll head up to 38k" feet. Why not stay at the same altitude for the flight? I know that using up fuel makes the plane lighter, but why would that matter with respect to the altitude the plane is flying?
A. We are always seeking the most efficient flight path in order to preserve fuel and protect the environment. Taking wind and turbulence out of the equation, we always strive to reach the highest altitude available based on our weight and outside temperature. The higher you fly, the less dense the air. As you fly in "thinner air" you will use less fuel because in order to keep a constant fuel to air ratio, the thinner air requires less fuel. On longer flights, as we burn a significant amount of fuel weight, it allows us to climb to even higher altitudes saving fuel and reducing emissions.
Q. It seems to me that the altitudes the pilots mention that we are flying these days are higher than they were when I was younger. (I seem to recall 25k being the norm.) How have flying altitudes changed over time? What is the maximum altitude that a commercial passenger plane could/should fly today? What is in the cards for the future?
A: As engine and wing design technologies have advanced, we have seen an increase in the altitudes that we can operate. When I started flying 40 years ago, 35,000 feet was considered about as high as we could go. We normally cruised in the high 20s or low 30s. There were exceptions. The Concorde SST would cruise above 60,000 feet, but that was in supersonic flight and a rarity. Now we operate at the high 30s and low 40s. Most commercial aircraft have a maximum altitude around 43,000 feet but they seldom fly that high.