SPRING is the time of year when many of us begin to think about booking holi­days — or, better still, start taking them. And many of us will be taking to the skies.

The best app in its field is FlightRadar24. This connects to public radar stations to give a live graphical display of all the aero­planes in the sky around you, over­laid on to a map. Clicking on one of the plane icons will bring up its flight number, departure-and-arrival airports, type, height, and speed; it can even produce a photo of the actual plane itself. It also shows a radar track of where the plane has been on its current jour­ney.

There are many apps that look at aeroplane movements; some are just for fun, others are useful for track­ing specific flights, and one can even send a text message to let you know that a particular flight has ar­rived.

The basic model is free, and comes with a useful range of facil­ities; but you can also subscribe to a silver level (£1.49 per month, or £9.99 per year) for an ad-free experience and additional flight in­­formation; or a gold level (£3.99 per month, or £33.99 per year) for addi­tional features, including weather layers, aeronautical charts, and 180 days of flight playbacks.

With all three packages you get AR Mode, the smartest part of the app. Rather than a graphical over­view of planes on a map, this mode activates the phone’s camera. You simply point it at the sky at an aero­plane, and it gives you all the in­­formation on the flight.

Another app takes this a step fur­ther. If you are a regular inter­national traveller you will probably be familiar with the following ex­­perience: you arrive in a new city in a new country, and you switch your phone on and have to wait five or ten minutes for the roaming net­work to connect before you can send a message saying that your plane has arrived safely.

Sometimes, it does not connect before you have to disembark, and, before you know it, you are in the immigration or customs area of the airport where phones should not be used; so you still cannot send a mes­sage to say that you have arrived.

This is where FlySMS comes in. This app monitors and keeps you updated on flights; but its core facil­ity is to send automatically text mes­sages that you have pre-prepared, to up to two people, to let them know when your plane has landed. Your phone does not need to be on, let alone connected to the roaming net­work, to work; simply set it up be­­fore you board your flight.

This app costs £5.99 per month for up to ten flights, or £38.99 per year for up to 100 flights.

The app ISS Spotter will show you the live position of the Inter­national Space Station (ISS) above the Earth at any particular moment — and let you know when it will next be visible from your location. The app ISS HD Live beams live streams from the ISS’s earth-facing camera direct to your phone or tab­let, providing some stunning views of our planet.