I read that the longest regularly scheduled commercial flight in the world is from Atlanta, GA to Johannesburg, South Africa, a distance of about 8421 statute miles.
The Boeing 747-400 has a maximum ranger of 8426 statute miles.
That seems to be cutting it a little close.
(There is an error on the page linked. The 7330 “statute” miles should actually be “nautical” miles.)
It says here that the “Longer-Range 747-400 (also known as 747-400ER)” has a range of “7,670 nautical miles (14,205 km)”.
This is just a WAG, but I’m guessing that since they are flying with the jet stream from Atlanta to Johannesburg, the actual flight time, and hence “range” covered, is considerably less than 8421 miles. I seriously doubt that they could then make the trip back from Johannesburg in a single flight.
Okay, some extra info…the jet streams at 30k feet regularly reach 200 mph, which, all told, would cut the flight time down by about 25%. Remember that the 8426 mile range is relative to the airflow around the airplane, so if the air around it is flowing at 200 mph it could actually go much much further than 8426 miles relative to the ground. Thus, with a 200 mph tailwind, it could probably complete the journey in under 6000-7000 “relative” miles, leaving plenty of fuel to spare.
Here’s the South African Airways’ flight schedule:
http://www.travelbeyond.com/airfares_africa/saa_flights.htm
Looks like hobbes730 is correct - the Atlanta to Johannesburg flight is nonstop, but the Johnannesburg to Atlanta flight stops at Cape Town and Ft. Lauderdale.
To address the fuel issue, long-range flights like this have to be “re-released” at some point along the journey. You are originally “released” when you depart the gate with the fuel required for the planned trip. This fuel takes into account such things as winds, temps, etc. At some point along the way (it depends on where your divert field is) you check your actual fuel burn against what was planned. You must have the planned amount of fuel or greater to continue the flight. If you do, you are “re-released” by dispatch to continue the flight. If not, you divert somewhere for more fuel.
Why would you not have the planned fuel? If you are only getting 50 knots of tailwind and you planned on 150, then you will be behind on the fuel burn, and in this case might not make Jo’berg. The winds aloft are only forecast, after all.
I seem to remember that long haul flights out of Jo-burg need to stop somewhere for refueling. This is because Jo-burg is like Denver/Mexico at some high altitude above sea level and they can’t take off fully fueled (insufficient lift available).
Maybe a commercial pilot can confirm this?
BwanaBob, that doesn’t seem correct…the highest cities in the world aren’t even half the altitude a 747 flies at. Thus, if a plane couldn’t even get off the ground because it had a fuel tank of gas, there’s no way it could ever get to cruising altitude.
I’m not a pilot though, so maybe I’m overlooking something 
Hehe, excuse me…I meant a full tank of gas. At any rate, if a 747 was filled with gas I don’t expect it would go much of anywhere
BwanaBob you are correct. Jo’Burg Jan Smuts Intl Airport is at 5559 ft elevation (1694 m).
hobbes730 the factor that you are overlooking is the runway. Runways are a fixed length, and the airplane must get airborne in that length of runway. Higher altitude (and higher temperature) decreases the performance of airplanes. Less thrust is available for a given power setting which results in a lower maximum takeoff gross weight. A heavier airplane takes longer to accelerate, which uses up more runway - eventually you reach a point where you would go off the end of the runway before you had sufficient airspeed to fly. (We won’t talk about stopping for simplicity’s sake).
As a comparison, try running a mile at sea level and then try doing it in Denver (or Jo’Burg, or anyplace over 5,000 ft). Thin air equals less performance.
The reason airplanes can fly at such high altitudes (ie 33,000 ft) is they already have built up the airspeed necessary at lower altitude and just use engine thrust to maintain speed and climb.
Taking off is a different story - you need to accelerate the jet to flying speed, which is also higher at higher altitude. If you built a runway on the top of Mt Everest and stuck a fully loaded 747-400 on it, my guess would be that the takeoff run would be about 20,000 or 25,000 ft - over 4 miles. Since it’s impractical to build runways that long, some compromises are made. The longest runway at Jo’Burg is 14,495 ft (4418 m). Given that length, some long-haul jets are limited as to their weight. They usually take a lower fuel load and stop somewhere for refueling, although they can also limit passengers and cargo.
Hope this helps!
True they’re nowhere near cruising altitude, but the thinness of the air at 1 mile altitude is significant.
I remembered where I heard this though; a fellow passenger on a JFK-SFO flight had connected from a Johannesburg flight and he told me that they refueled in Dakar because they couldn’t fully fuel the plane because at J’Burg altitude the plane couldn’t achieve sufficient lift if fully loaded and fueled.
Maybe he was full of bs…
pilot141
Thanks for the confirmation (my lastpost criscc-crossed yours!)
Has anyone considered the “great circle” routes that airliners use? You know, since the world is spherical, the shortest distance between two points isn’t a straight line?
Or is this hidden in the definition of “statute mile” somewhere?
No. Whether statute or nautical mile, it has no bearing on the course used. This site gives the great circle distance as exactly 8421 statute miles, 7318 nautical miles.
If it weren’t a great circle distance, it would have to be through the Earth’s crust.
I have friends that regularly visit their families in South Africa. They fly New York to either Johannesburg or Cape Town (I forget which, and they have family in both places.)
They say that the flight from NY to SA is usually non-stop, but on the way back they stop at a small Atlantic island to refuel (I believe Cape Verdi).
Just one addition to make. The max range quoted for an airliner would take into account having the required reserve fuel remaining in the fuel tanks. It wold be a range that you can plan a flight on, not a range where the engines stop once you reach it.
I’ve seen that situation in some low-altitude but small airports too. You can take a direct flight from Tokyo to Kona Int’l Airport on Hawaii Island, but the runway is too short to take off of with a full load of fuel. So the return flight stops at Honolulu.