Backfire From Germany, joined Oct 2006, 0 posts, RR: 0
Reply 2, posted (11 years 10 months 4 weeks 14 hours ago) and read 1130 times:
It's almost certainly to do with the head/tailwinds. You can easily knock as much as an hour off a transatlantic flight if the winds are with you -- especially if the course optimisation to maximise a wind advantage also happens to minimise the distances involved. Don't forget that aircraft will usually fly offset to the great-circle distance because the wind advantage more than compensates for the additional flight distance.
So, if the plane has to catch up a delay, the MTT might be the most sensible option - the direct cost is higher, but it might save some people´s connecting flights. If the flight is on time, the MTT would be pointless, so you choose the MCT, which gives you longer flying times etc.
B737-700 From , joined Dec 1969, posts, RR:
Reply 5, posted (11 years 10 months 4 weeks 10 hours ago) and read 1077 times:
I am pretty sure it has to do with that when flying at maximum speed you burn more fuel than when flying at a lower speed.
So e.g. cruising at Mach 0.82 gives you a longer flying time, than cruising at Mach 0.86 but therefore burns less fuel. Same as in your car. When travelling at maximum speed you naturally get to your destination faster but you also need more fuel.
Airsicknessbag From Germany, joined Aug 2000, 4723 posts, RR: 34
Reply 6, posted (11 years 10 months 4 weeks 10 hours ago) and read 1072 times:
Yup, B737-700 summed it up pretty neat.
Another factor that comes into the equation are fees you have to pay to a country for overflying it. If you have a country which asks for high fees (e.g. Iran if I remember correctly), you might have the option to circumvent it - hence you leave the MTT in order to save money, the MCT might lead around that particular country.
Ragousis From United States of America, joined Dec 2000, 30 posts, RR: 0
Reply 8, posted (11 years 10 months 4 weeks 7 hours ago) and read 1036 times:
backfire, because all planes, trains, boats, cars etc have a speed called max range, if you go above this speed your fuel burn per mile traveled go up. For example a plane burns 500 gal per hour at 500 knots (max range speed), at 550 knots the plane burns 600 gal per hour. If you do the math a 1000 mile trip takes 2 hours at 500 knots and 1.8 hours at 550 knots. We know the burn rate per hour, so we get 1000 gal used in the first case (500 knots) and 1080 gal used in the second case (550 knots). All because cruise speed does not vary proportionate with fuel burn per mile traveled. And who told you cars travel more efficient at higher speeds? If by high speed you mean 45 mph then you are correct. Because for most cars if you are above that speed your fuel burn per mile traveled will go up. I do have a degree in Aerospace Engineering so I have done the research on this. If you want more evidence I can get out my 727 manual that has all the performance figures.
J-bird From Canada, joined Feb 2001, 107 posts, RR: 0
Reply 10, posted (11 years 10 months 4 weeks 4 hours ago) and read 982 times:
There was actually a pretty good Discovery Channel Europe program called "The Flight" about two months ago that covered this. The program followed an Air Canada flight from Toronto to Frankfurt, and investigated the entire flight planning, execution and completion process.
A significant portion of the pre-flight preparation was dedicated to choosing which Atlantic track to request from Atlantic Control. Among the many variables considered were flight time, fuel burn and congestion on each track. Thus, it seems that while the time versus cost argument is carefully considered by the airline, the congestion factor plays into it quite extensively in that a particular route track request from an airline may not be approved by Atlantic Control. I would suspect the same is true for other busy airspace around the world too.
Also interesting to note that it is often cheaper for an airline to fly the maximum speed track, despite the extra fuel burn, in order to avoid having to accomodate passengers who missed connections. In the program I mentioned above, this was the case with the AC flight, which needed to get 15 passengers with close connections on the ground to avoid the cost of putting them up or otherwise dealing with them.