"Lets Fly" by Matthew Martino Designs and Lets Fly Academy is a fascinating iPhone and iPad app for airplane enthusiasts and travellers, as well as serious student pilots alike.
The author has also published a book - "Let's Fly" - but both book and app are standalone and one does not require the other.
The app takes interested readers through just how flight works, covering altitude, airspeed, the magnetic compass, aerodynamics, axes, the forces which act on a plane, radiotelephony and the phoentic alphabet.
The app provides tips for students studying for their private pilot license (PPL) as well as curriculum vitae advice for new and experienced pilots.
The app includes six tests to challenge your understanding of flight, as well as details of flight schools within the UK.
Rounding it all of nicely is a slideshow with 50 photographs of a range of aircraft from propellor planes to large passenger jets.
Really, this is a friendly and enjoyable app. It is free and contains no in-app purchases or hidden charges.