What's best iPhone app for flight tracker?

Hi everyone I'm Mario, I have question on anyone that knows about iPhone apps, my grandparents our coming back from Puerto Rico soon, I was wandering what's app that can track where at on plane, like anything that can help me know where there flight is?

The Google Search app is surprisingly good.

However the best app is Safari, and you go to your Airport's webpage and type in the flight number that they are flying on. It says on their ticket.

Flight track or Flight Track Pro… Same company, one is free the other is pay

http://www.mobiata.com/apps/flighttrack-iphone