FlightRadar24 is described as 'Flightradar24 allows you to track:' and is an app in the Travel & Location category. There are more than 10 alternatives to FlightRadar24 for a variety of platforms, including Online / Web-based, Windows, Linux, SaaS and iPhone. The best alternative is RadarBox, which is free. Other great apps like FlightRadar24 are FlightAware (Free), PlanePlotter (Paid), ADSBExchange (Free) and adsbScope (Free Personal).
PlanePlotter receives and decodes live digital position reports from aircraft and plots them on a chart. You can see a radar-like display of all those aircraft around you broadcasting digital messages including ACARS, ADS-B and HFDL.
The world’s largest co-op of ADS-B/Mode S/MLAT feeders, and the world’s largest public source of unfiltered flight data. Access to worldwide flight tracking data for hobbyists, researchers, and journalists alike.
The adsbSCOPE software is another free ADS-B radar program with network sharing options. You can download ADS-B data which is shared by other adsbSCOPE users to augment your own local radar setup. This allows you to have a global air radar.
Open source project displaying aircrafts, ships or trackers on 2D/3D map. Browse through the data based on a particular aircraft, airline, airport or vessel to search through the database or see extensive statistics. Can use many data sources.
The OpenSky Network is a non-profit ADS-B exchange for sharing real time aircraft data broadcast over the airwaves. The network consists of thousands of sensors connected to the Internet by volunteers which collect ADS-B and Mode S broadcast data.