FlightAware.com is a free flight tracker which tracks both commercial and private aircrafts across the world. Founded in 2005, FlightAware has become the leading source of flight information across the world.
Once you visit the site, all you have to do is to enter the Airline Name and Flight No. and the site will magically show you the current status of the aircraft – even if it is mid-air. You may browse flight data by Operator, Aircraft Type and Airport. The interface is quite simple and easy to understand for the lay person while advanced options are available for the geeks.
FlightAware also has an Android App with the same name, which is very convenient to use. You can even receive real-time push notification flight alerts, view airport delays, see nearby flights (in the air!) and more.
Remember to look up FlightAware if you are travelling or assisting someone who travels by air.