As you may know, FlightGear is the most popular, open-source, flight simulator, running on Linux.
It is a realistic game, being played by both normal users and future airline pilots, because of its accurate details. It allows the user to fly aircrafts, helicopters, airliners or modern combat aircrafts on many tracks.
The latest version available is FlightGear 2016.1.1, which brings an integrated launcher, a reduction in the installation package size and both performance and rendering improvements.
Up to date packages are available via some third party PPA, so installing the game on Ubuntu is easy. Just add the PPA to your system, update the local repository index and install the flightgear package:
$ sudo add-apt-repository ppa:saiarcot895/flightgear
$ sudo apt-get update
$ sudo apt-get install flightgear
Optional, to remove flightgear, do:
$ sudo apt-get remove flightgear
The installation instructions should work on Ubuntu 15.04 Vivid Vervet, Ubuntu 14.10 Utopic Unicorn, Ubuntu 14.04 Trusty Tahr, Ubuntu 12.04 Precise Pangolin, Linux Mint 17.2 Rafaela, Linux Mint 17.1 Rebecca, Linux Mint 17 Qiana, Linux Mint 13 Maya, Pinguy OS 14.04, Elementary OS 0.3 Freya, Elementary OS 0.2 Luna, Deepin 2014, Peppermint 6, Peppermitn 5, LXLE 14.04 and Linux Lite 2.