
Ryanair, Hamiltonian Cycles, and using graph theory to find cheap flights (2018) - jonluca
https://blog.jldc.me/posts/ryan-air?ref=hnm20
======
dang
This had a big thread just a few months ago
([https://news.ycombinator.com/item?id=22100736](https://news.ycombinator.com/item?id=22100736))
so this repost is clearly a dupe. Please see
[https://news.ycombinator.com/newsfaq.html](https://news.ycombinator.com/newsfaq.html).

There was also a big thread at the time (2018):
[https://news.ycombinator.com/item?id=18526261](https://news.ycombinator.com/item?id=18526261).
Since the cutoff is about a year, that repost was ok, but the current one was
not ok.

~~~
jonluca
Gotcha, thanks! Will keep the 1 year rule in mind

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stormdennis
I don't love Ryanair but the people who criticise them remind me of the Woody
Allen joke about the diners complaining about the restaurant, "The food was
terrible and the portions! So small!"

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fatnoah
>Ryanair is a wonderful example of two extremes - it’s one of the worst
possible airlines that nickel and dimes you for everything, it’s not a great
employer, and it is rated the worst European airline; however, it’s dirt
cheap.

This is an interesting conclusion. I would say that being cheap and terrible
are not two extremes, but the same one.

~~~
tathougies
Am I the only one that loves Ryan air. Great, no-nonsense pricing, no-nonsense
service, and they do exactly what you pay them for.

~~~
madaxe_again
Not always. I’ve spent 36 hours stuck at a gate with no plane in sight with
them, before they finally cancelled the flight - mechanical issues with the
aircraft, apparently - and they _always_ find a way to worm out of the EC
compensation directive, mostly by just flatly refusing to engage. Still
waiting for the refund, nearly a year on - they give themselves 250 _working_
days to issue refunds.

They also have poorly trained pilots, who either aren’t qualified for ILS or
aren’t confident in poor conditions - on numerous occasions I’ve been on
flights which they’ve diverted (Bristol becomes Birmingham, Bergerac becomes
Toulouse, Porto becomes Madrid) because of weather, while other airlines land
and take off without issue.

~~~
throwawayflyboy
> They also have poorly trained pilots, who either aren’t qualified for ILS or
> aren’t confident in poor conditions - on numerous occasions I’ve been on
> flights which they’ve diverted (Bristol becomes Birmingham, Bergerac becomes
> Toulouse, Porto becomes Madrid) because of weather, while other airlines
> land and take off without issue.

This is straight-up defamatory. Ryanair have similar entry requirements to the
majors, much better training and equipment, and the best safety record of any
airline in the world. No one gets an EASA Part FCL without ILS, and every
Ryanair pilot will be absolutely confident in ILS approaches - most will have
done far more than other airline pilots.

~~~
Retric
Ryanair is simply a young airline that only recently grew in size. Their
safety record is practically blank and hardly qualifies them as the best in
the business.

Hawaii Airlines for example has not had a single fatal crash since it’s
founding in 1929.

~~~
donaltroddyn
Ryanair is 34 years old and flew more PAX in the last two years than Hawaiian
has in its entire history, with significantly fewer accidents and incidents,
even if you only consider those that occurred while both airlines were flying.
It's hard to find historical PAX numbers for Hawaiian, but it seems that
Ryanair overtook them at some point in 2000.

I don't see any basis for your claim that their safety record is "practically
blank". They are widely considered the world's safest airline - a spot they
shared with Southwest until ‎SWA1380.

~~~
Retric
If you compare crashes per flight by year, the entire industry has become
safer over time. The expected number of crashes given their operating history
assuming an average airline would likely be zero. In fact over 20 major
airlines currently having a clean record. So, on it’s own that’s really not
enough information to say anything.

If we are trying to find ‘the best’ airline in the industry you need to either
consider only current practices/equipment etc, or look for airlines with zero
crashes despite higher expected lifetime risks.

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bmc7505
There was a discussion here the other day about the Seven Bridges of
Königsberg, which is today known as a Eulerian path. [1]

Unlike Eulerian paths, which are detectable in linear time [2], detecting
Hamiltonian paths is NP-complete [3]. Does anyone have an intuitive
explanation for why this is the case?

[1]:
[https://news.ycombinator.com/item?id=23123754](https://news.ycombinator.com/item?id=23123754)

[2]:
[https://en.wikipedia.org/wiki/Eulerian_path#Hierholzer's_alg...](https://en.wikipedia.org/wiki/Eulerian_path#Hierholzer's_algorithm)

[3]:
[https://en.wikipedia.org/wiki/Hamiltonian_path](https://en.wikipedia.org/wiki/Hamiltonian_path)

~~~
jcranmer
> Does anyone have an intuitive explanation for why this is the case?

Imagine building a Eulerian path. You're standing at a node, trying to figure
out which edge to go down next. Eventually, because it's a Eulerian path,
you'll have to go down all the edges eventually. This means it doesn't matter
which edge you go down--even if your path hits a dead end, you can magically
go back in time and patch in a cycle to your original path.

Put another way, if you establish that a graph has a Eulerian path, every
maximal set of edge-disjoint cycles in the graph constitutes that path. Just
by looking and making decisions at a very localized context (every node), you
can formulate a correct answer.

By contrast, Hamiltonian paths are rarer. Only some maximal sets of node-
disjoint cycles can be combined to construct a Hamiltonian path. You don't
have the property that you can trivially patch the cycles together if you make
a mistake. Looking at a node and trying to decide which next node to pick,
you'd have to understand the structure of the entire graph very well to
understand if traversing to A will screw you up, and the ramifications are not
local.

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vmception
Ryanair can only possibly be the worst rated European airline because everyone
uses it. There are plenty of budget airlines between obscure routes in Europe
that are the same caliber.

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stormdennis
Thanks to Ryanair a flight that started at 140 pounds in 1986 can be had for
less that 20 today.i know someone who had to pay 400 for it when they needed
to get to a funeral.

~~~
switch007
That is in no way an apples to apples comparison.

£140 would have probably included things like baggage, more leg room, perhaps
less restrictive ticket terms and food on a full service airline with eg
better IRROPS handling.

~~~
stormdennis
Believe it or not it's a half hour flight, (the alternative is a ferry and
drive/bus). It was a scandal what inefficient national carriers were able to
get away with in those days. Most people had to do the long bus trip, 15 hours
because flying was too expensive.

~~~
switch007
Thanks for the sarcasm but yes I do believe it. That's a different topic
though.

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dragosmocrii
I had a technical assignment with an online air tickets seller, and the
requirement was to build the backend for a service that will find routes
between airports. aboy was it a fun assignment. As the nodes increase, the
time to search the graph for routes increases exponentially. non stop routes
would yield the result in milliseconds, 1 stop about 1 second, 2 stops around
40 seconds, 3 stops about 4 minutes, 4 stops.. well I didn't wait for that :)
I had engineered a dataset of flights and airports from a puclic source, for a
couple thousands airports, and a couple tens of thousands of flights. graph
theory is very interesting subject. Turns out, my solution was overkill, and I
got the job, but 2 months later Corona happened, so now I'm back to
freelancing :D

* If you're curious about the implementation, see [https://github.com/DragosMocrii/flights-search-app](https://github.com/DragosMocrii/flights-search-app)

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joyj2nd
My experience with Ryanair ist pretty good. If (big if) you know what to
expect. I had terrible experiences with Wizz and United and avoid them like
the plague.

Ryanair is cheap. Tickets can be 9.99, 12.99 Euros. (One Way). I have often
speculatively bought these tickets for a trip that might or might not occur
and then let them expire. Obviously this is part of their business strategy.

But Ryanair is great.

By the way, Kiwi.com also searches flights with Ryanair connecting flights
(AKA Flight hacks). They once offered me a 50 Euros trip from Duesseldorf to
Malta with 5 tickets, including going to Bucharest, Berlin etc. I would have
been on the road/in the air for two days.

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JadeNB
I forget how long we ask for between duplicates, so maybe it's OK, but this
also appeared closer to when it was written:
[https://news.ycombinator.com/item?id=18526261](https://news.ycombinator.com/item?id=18526261)
.

~~~
dang
The cutoff is about a year
([https://news.ycombinator.com/newsfaq.html](https://news.ycombinator.com/newsfaq.html)).
However, there was also a major thread a few months ago, so this is clearly a
dupe. More explanation here:
[https://news.ycombinator.com/item?id=23146996](https://news.ycombinator.com/item?id=23146996)

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krn
Ryanair is like McDonald's of air travel. I have taken well over 50 flights
with them over the last decade, and never had a bad experience, because I
always knew what to expect.

In general, it's not worth paying more than 50-60 EUR for a one-way ticket,
and it's not worth expecting any compensations or support if something goes
wrong.

Nobody expects a restaurant experience from a fast-food chain.

~~~
5etho
the thing is, thanks to eu you have a support, also legal rights as every
airline

~~~
krn
In theory, yes. In practice, it would often cost more in time to actually
obtain anything from a low-cost airline in Europe than the compensation was
worth.

I strongly believe that if one wants the level of customer service of a
traditional airline, (s)he should be flying with a traditional airline, – and
paying for it.

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saadalem
Reminds me a little bit of Exploring the Complexity of Driving Directions

[https://jsomers.net/blog/directions](https://jsomers.net/blog/directions)

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agustif
Ryanair is like Gmail, the more the price of something tends to zero, the more
you're ready to put up with bullshit like (Google reading your mail, or
obnoxious ads on your inbox, etc)

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charlus
I always really enjoy reading graph algorithm pieces, and similarly after
studying them have never actually used them. A really nice approach to a fun
problem.

