Not OP but I have 0. I travel maybe 1-3 times a year and I usually install it for the trip then delete it.

Airports/flight/airlines are PRIME candidates for Progressive Web Apps.

Here's the ones I use most often: Avinor (Norwegian airport authority), Schiphol (Closest hub), Kastrup/Copenhagen (#2 hub (of sorts)) and Frankfurt.

Then there's all sorts of second tier airports which have their own apps of sorts - say, even Dyce (Aberdeen) has one, though I am not sure it is an official product.

Add to that that any airline worth its salt has got at least one app, and it soon adds up...

I've found Kayak's app to be pretty useful + up to date for tracking flights. You can input a flight number, or search for flights based on departure and arrival airport. I haven't found any other app that reacts to delays or gate changes as quickly. I believe they get their data by aggregating a lot of individual sources (https://www.quora.com/How-does-Kayak-get-all-information-fro...)

https://itunes.apple.com/us/app/kayak-flights-hotels-cars/id...