It was reported recently that the Swiss flight LX18 from Zurich to New York had detected an engine issue shortly after take-off and decided to land back in Zurich.

Apparently, the Airbus A330-343 cannot just dump the fuel and, fully tanked, was too heavy to land safely, so it had to fly for 5 hours in a loop just to burn the excess kerosene.

Would it have been too complicated to implement a fuel draining mechanism? What would have happened if they couldn't fly for 5 hours and had to emergency land right away? Wouldn't this inability to drop fuel be a safety hazard?

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    $\begingroup$ Closely related: Why doesn't the 737 have a fuel dump nozzle? $\endgroup$ Commented Aug 20, 2019 at 23:20
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    $\begingroup$ I would also guess that in densly populated Switzerland with its strict environmental protection rules such a thing as dropping fuel would be considered illegal and would result in a high penalty for the airline. $\endgroup$
    – Christoph
    Commented Aug 21, 2019 at 15:20
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    $\begingroup$ @Christoph: they could drop it in Germany, couldn't they? Jokes by side, when you drop fuel it dissipates, it's not as if people on the ground were bathed in jet fuel all of a sudden. $\endgroup$ Commented Aug 21, 2019 at 17:55
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    $\begingroup$ I'm a bit surprised that neither of the answers actually address the title question being asked at this time: they both go on about why an overweight landing should be avoided, but not why the A330 doesn't have the ability to dump fuel like some competing airliners. $\endgroup$
    – 0xdd
    Commented Aug 22, 2019 at 14:40
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    $\begingroup$ Somehow I'm not sure whether dumping it is better for the environment than burning it? $\endgroup$
    – user42493
    Commented Aug 23, 2019 at 0:14

3 Answers 3


To supplement Jimmy's answer, if they had to land right away, they could have; it just would've resulted in an overweight landing being recorded, and which on most airliners triggers a special inspection of the landing gear and its attaching structure, and if nothing is permanently bent or cracked or broken, you are good to go.

An overweight landing in itself shouldn't result in damage unless the landing was hard, the overweight condition using up some of the structural safety margin, and if you know you are landing overweight you will take extra care to land smoothly.

Depending on the airplane, an overweight landing may apply a "penalty" so to speak, accelerating some inspection interval, or advancing a life limit on a structural component in the gear, or some other negative impact maintenance cost wise. So there may be a significant incentive to avoid it from a long term cost perspective even if it means wasting 5 hours of fuel going round and round in a hold.

In the case mentioned, the crew would have consulted with the airline's Maintenance Control organization on the private company radio frequency to discuss whether to land overweight or not, and if there wasn't an urgent need to land, the Capt would have agreed with Maint Control and burn off the fuel to avoid the overweight landing and its ramifications.

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    $\begingroup$ On a commercial flight, is such a cost consideration (safety issues aside) a legitimate justification to keep passengers delayed for 5 hours? $\endgroup$
    – JBentley
    Commented Aug 21, 2019 at 12:24
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    $\begingroup$ Yes. Same reason Maintenance Control will advise a crew to divert an airplane to airport X even though pax might prefer Y, because the airline has facilities at X. $\endgroup$
    – John K
    Commented Aug 21, 2019 at 12:49
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    $\begingroup$ I usually wonder, if they thought they were OK to fly in circles for 5 hours, why not fly towards your destination for the same 5 hours? They could even alter their route to always be within a reasonable distance of runway able to support them landing. $\endgroup$
    – SnakeDoc
    Commented Aug 21, 2019 at 17:29
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    $\begingroup$ @SnakeDoc The route from Zurich to New York might not "always be within a reasonable distance of [a] runway" (where that distance is shorter than usual) and 5 hours into an altered route might have them landing on some ice patch in the North Atlantic where services and spare parts might be hard to find. $\endgroup$
    – WBT
    Commented Aug 21, 2019 at 18:14
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    $\begingroup$ Flying "toward" (but not actually to) your destination may be worse for passengers. Returning to the origin may mean returning to the airline's hub (Zurich) in this case, where they have facilities, staff, and are best positioned to arrange alternate flights and/or a new aircraft and crew. Taking passengers to another location may strand them somewhere without these resources (or worse, somewhere in the arctic). That's completely worth it if there's an emergency need to land there, but returning to the origin, especially if it's the airline's hub, is ultimately more convenient for everyone. $\endgroup$ Commented Aug 23, 2019 at 2:10

I think the characterization that it's "too heavy to land safely" is erroneous; the fuel burning is probably out of circumspection and to allow for a better safety margin. The runway length may also be beyond the landing field length and/or the brake energy limit of the heavy weight, so decreasing weight would add to the safety if immediate return to land is not absolutely needed.

14CFR 25.473 requires that landing gear and supporting structures withstand a landing load at maximum takeoff weight at a contact speed of 6 ft/s. This is definitely reduced from the 10 ft/s design load for maximum landing weight, but is still larger than the typical landing speed of 2-4 ft/s. As I understand it, this requirement applies whether or not the aircraft has fuel dumping capability. Therefore, the aircraft has the immediate return to land capability, at least from a structures perspective.

So where does maximum landing weight and fuel dumping come in? On top of the distinction above, it is primarily a climb performance limitation as per 14CFR 25.1001: if the aircraft does not have a fuel dumping system, it must meet the all-engine-operating and one-engine-inoperative climb in the approach climb configuration at maximum takeoff weight. Otherwise, credit can be taken for maximum landing weight. So the design decision of whether incorporating a fuel jettisoning system or not comes down to this.

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    $\begingroup$ There may be some additional burdens, like EPA fines for dumping fuel in flight in the US. I don't recall reading anything in particular, but it seems like something one of several government agencies may have purview over. $\endgroup$
    – jww
    Commented Aug 23, 2019 at 7:40

Also consider the location. Assuming the a/c can do so, there would be no issue (apart from pollution) in dumping fuel over sea. But you want to spray jet-A all over Zurich? Plenty of ignition sources on the ground. Really not good.

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    $\begingroup$ Jet fuel vaporises long before reaching the surface, be it land or sea. :) $\endgroup$
    – user18035
    Commented Aug 21, 2019 at 11:00
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    $\begingroup$ Also jet fuel is quite hard to ignite, except in controlled conditions. For example dropping a lighted cigarette into a bucket of Jet-A has exactly the same effect as dropping it into a bucket of water. $\endgroup$
    – alephzero
    Commented Aug 21, 2019 at 11:31
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    $\begingroup$ @bogl D Brooks was concerned about ignition sources, which, as ClobberXD and alephzero mentioned, isn't actually an issue. Nevertheless, fuel dumping is always done away from population centers, because the airline operators don't want to dump fuel on their customers. $\endgroup$ Commented Aug 21, 2019 at 14:20
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    $\begingroup$ @alephzero there's perhaps an interesting question there: I've seen those youtube ATC videos where they get a plane out a ways from a city before dumping fuel and then vector traffic around the area for a while after. How close (in time, in distance) to the dump would another plane need to fly before it would actually be in danger? $\endgroup$
    – mbrig
    Commented Aug 21, 2019 at 16:45
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    $\begingroup$ @mbrig Feel free to ask that question by hitting the Ask Question button. $\endgroup$
    – PerlDuck
    Commented Aug 21, 2019 at 17:32

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