By: AirTraveller PH Staff
You take a Philippine Airlines non-stop flight from Manila to Los Angeles on board a Boeing 777-300ER. You depart Manila and arrive in Los Angeles according to schedule and you noticed the trip duration was 12 hours. However on your return flight from Los Angeles to Manila using the same aircraft (B777-300ER), you noticed that the flight duration was 15 hours and 30 mins? Why was this so?
The flight utilized the same aircraft type (B777-300ER), didn't stop anywhere, and just flew Los Angeles to Manila without any diversions. Why was the Eastbound flight 3 hours shorter than the westbound flight?
Same thing goes for Manila to New York flights. Utilizing an Airbus A350-900, PR126 Manila to New York takes 15 hours and 33 minutes but PR127 from New York to Manila utilizing the same aircraft takes 16 hours and 50 minutes!
These do not only happen in PAL flights but to all flights around the world as well.
The reason why westbound flights (US to Manila) take longer than eastbound (Manila to US) is due to the rotation of the Earth.
The Earth rotates on its axis at about 0.0005mph, but at the surface ang Equator, the rotational velocity is about 1,040 from West to East. The Earth only rotates in one direction and that is West to East. With this, it may seem like an aircraft moving from East to West should take shorter than that moving West to East since the Earth's rotation is like "pulling" the destination closer. This is not the case though. There are other factors.
Not only does the surface rotate, the atmosphere goes with it as well. This influences the wind patterns above the Earth, also known as high-altitude jet streams.
A rotating object has a force perpendicular to the axis of rotation known as the Coriolis force. This force pushes winds to the east in the northern hemisphere and to the west in the southern hemisphere. The strength of this force is relative to the surface speed rotation of the Earth.
The winds are also affected by solar heating which flow from areas of high pressure to low pressure. Combined, these effects produce jet streams that move from west to east, but with a bouncing pattern. The jet stream can vary in strength, altitude and routing over time and of which are usually strongest when closer to the poles.
Airlines study the jet stream patterns every day for which they decide which routes to take. If an airplane flying from Manila to the US over the Pacific Ocean can piggy back on a strong tailwind moving Eastward, it will take that route even if they would have to fly a longer physical distance. Flying with the jet stream not only allows faster flight duration, but it also saves on fuel. The time difference is indeed huge. However, a US to Manila (Westward) flight paints a different picture as it flies against the jet stream. This takes more fuel and longer flying time, hence, airlines constantly look for a route to avoid some of the effects of this jet stream.
Below is a comparison of two PAL flights, PR102 and 103. PR102 flew from Manila to Los Angeles and the other is PR103 which flew from Los Angeles to Manila.
Both utilized the same Boeing 777-300ER aircraft on January 20 but PR102's flight time was 11 hours 24 minutes whereas PR103 took 14 hours and 52 minutes. Notice that the Eastbound flight from Manila to the United States flew closer to the pole whereas the Westbound flight from the United States to Manila flew closer to the equator. PR102 flew along with the jet stream whereas PR103 flew against the jet stream moving westward.
Before the Boeing 777-300ER came into service with the airline, PAL used the classic Boeing 747-400 to fly the same route. The trip from Manila to the US was non-stop even at full load. The trip back to Manila however was different. There are times the flight would have to make stopovers in Guam to refuel and sometimes, none. PR103 during that time would depart Los Angeles at around 7:00pm to 8:00pm which include a stopver at Guam before landing in Manila. If PR103 would be delayed until 10:00pm or so Los Angeles time, there is a huge chance that the 747-400 would not be making a refueling stop in Guam as the route to be taken would not encounter strong tail winds.
Again, this is does not only go for PAL flights but for all flights around the world, regardless of which country, route, and destination. Some were just wondering why PAL flights from Manila to United States were shorter in terms of flight time as compared to the return flight.
We hope this answers your question.