why do the airplanes sometimes go the other direction?

Question

I live near Harry Reid Airport (FKA McCarren airport) in Las Vegas, directly west of the airport. My apartment faces west. The vast majority of the time, I can look out my window or walk my dog and see planes lined up to come in for a landing (sometimes 7 or more at once!) and watch them fly eastward overhead on their descent. But sometimes, every now and then, the planes go the opposite direction and I see them going WEST and gaining altitude (so clearly they have taken off). WHY do they seemingly randomly switch the runway direction? Weather and wind does not seem to play any factor as I’ve tried to pay attention to if I only see them going the other way when it’s cloudy or windy and no… It truly seems random. Why do they do this? It baffles me.

In: 49

Answer 1

The only thing we can sure of is that it’s not random. There are multiple factors that air traffic control (ATC) uses to determine the appropriate runway(s) to use for departures and landings, the biggest being wind direction and speed. At the airport in my city, landing to the southeast is preferred because of mountains and because it’s the runway with the ILS (instrument landing system) approach. Also, we have a lot of flights that are eastbound. So they’ll prefer use this runway, even if there’s a slight tailwind, instead of going the opposite way on the same strip of concrete, to the northwest.

I can’t figure out why ATC would have the majority of landings (and therefore takeoffs) to the east at Harry Reid. Commercial airliners at busy airports, even in good weather, fly instrument-guided approaches (known as “instrument approaches” or “instrument approach procedures”), and only one out of the 13 such procedures at Harry Reid are for an east-pointing runway. This tells me that surface winds out of the east at Harry Reid are uncommon. The only way I can explain this is that you’re not straight west of the airport. Are you in the Spring Valley/Sovana area, or perhaps over by Whitney? If you’re in the North Las Vegas area, then there’s an almost straight-in approach to runway 19L.