On july 25th 2019 I decided to make flight search engine and include al my favourite tools and features I find scattered around all different web sites, services, apps, plugins and Telegram bots (most of them are mentioned in my Dutch book on flying cheap called Thuisblijven is duurder).

Check the project here.

I have some experience in HTML/CSS and none in JavaScript. I am thankful for my friends helping me out.

Check the version updates below to see my progress.

Version 0.10 New design

I went back and forth with multiple designs and now decided on showing flights vertically, while still focusing on stops (I think they’re very important for travelers). Some difficulties for now include getting times over different time zones right.

Version 0.9 New features — August 8

I added some basic functionality like choosing cabins (also, allowed for multiple options). Furthermore, I’ve added a spinner to indicate Yelmair is searching, I’ve added an option to include minimum stopover time (to enhance stopover experiences), I made results collapsable and redesigned results.

Version 0.8 Toggling — August 5

Learning for a day really paid off. I made a oneway/return toggle and hopefully fixed the datepicker. With lots of if’s and var’s I managed to get it to work. You can now search for oneway tickets and return tickets using the same date picker. Also, the alliance toggles work now.

I uploaded this version to

Learning — August 4

With some help and googling I set up a basic search engine but things went a bit too fast for me. So I decided to read up on JavaScript on W3Schools to understand my own code.

Beta (not really) — August 3

I shared some screenshots on Twitter and Instagram, but it would be better if people could already test this early version, right? So I decided to upload a simple .html-file to

I still don’t have an SSL-certificate, so I’m live but not really.

Version 0.7 Stopover extras — August 2

Some airlines offer free stopover hotels, city tours and other extras when travelers have a stopover of 6 or 8 or 9 hours or more (but less than 24 hours). I want to show this in search results. This is not only logic, but needs some extra data. In all these cases, flights on both ends of the stopover have to be with the same airline, so for now Yelmair only shows a text when this is the case. I still have to add lots of other information. My friend Piet helped me with this feature.

Version 0.6 Stopover images — August 1

Since this coding stuff is new for me, I decided to try with another API. Just for fun I wanted to show a picture of the stopover city between flights. In theory this is easy to do: Kiwi gives me the city name. I take that city name and feed it to the Unsplash API and that returns the first search result with the city name as a query. My friend Marc built this feature, because it can only run after the flights are being shown. Still, I don’t know how this works.

Version 0.5 Yelmair — July 31

I decided to name the feature Yelmair. Of course after my first name Jelmer, which is a Dutch name that nobody outside the Netherlands ever understood the first time. I was once called Guilhermo in Mexico though.

Version 0.4 Miles — July 29

One of the main features I wanted my flight search engine to have is a way to display booking class and number of miles to earn, based on this booking class (as well as airline and distance). Flight search engines almost never show this class (for example booking class Y) and also never show how many miles to earn. Kiwi gives me this booking class information and the API of Wheretocredit tells me, based on the airline, distance and booking class, how many miles can be earned with different frequent flyer programs.

The difficulty here is that the results are shown first and I can yet only show miles afterwards. This is why I only show a button with the text ‘Where to credit’ for now. This feature was made with the help of my brother Jasper.

Version 0.3 Maps — July 28

I wanted to learn how to use JavaScript to show content. That’s why I set up a generated Great Circle Map image URL with depart and return IATA-codes of airports. Kiwi gives me a result, which is then added to the URL and displays an image with the flight route.

Version 0.2: Flexibility — July 27

Since the Kiwi API lets users search flexible dates, I decided to add a depart period and return period. Users can fill in four dates (two to set the depart period and two to set the return period) between which Kiwi then searches for the most cheap flight.

Version 0.1: Basic set-up — July 26

I used the Kiwi API to make a simple search engine. I learned how to send a request and receive data, which I can show. With the help of friends Marko, Piet, Flowen and Jasper I set up the most simple way to search flights: use IATA codes for airports (three letters, for example AMS for Amsterdam) and airlines (two digits, for example EK for Emirates) and date inputfields for depart and return flights.

Users can search for flights and now I only show the top 5 trips Kiwi returns. They’re being show including flight time and stopover time.

Version 0: Idea — July 25

This is my idea: to make a search engine for flights, with all the features and benefits needed by travelers. I’m not focusing on the 95% of travelers that don’t want to go from A to B in the most efficient way. My target audience is the other 5% that gets excited to see new places, loves long stopovers in interesting cities, wants to explore the world and takes trips based on an urge for adventure.