Flight tracking programs

Two of my kids are traveling to Europe tonight to perform with a concert band and see the sights. My oldest child did this trip two years ago and I remember being able to track the flight in real time through some website. I can't remember the site. Any suggestions on good sites for this?

 

I ended up using http://www.aeroseek.com/webtrax/ which worked OK until the plane got about halfway across the Atlantic. After that I got no further updates. I'm guessing it gets its info from the FAA which wouldn't apply in Europe. I tried various other programs that my google search suggested, but had no luck. I'm surprised that some European website doesn't have this service. Oh well, when they come home in a few weeks, I'll be able to track them once they get into US airspace.