during a p.e lesson at school today near heathrow airport i couldnt help but just notice a air canada a340 on finals as it got closer to the runway just before dissapearing under the trees a bright white light came on (rather like a landing light) but then turned off and after another a340 on approach done the same thing but it was on...off..on..off it was a very bright light from the right hand side seemed like it was coming from the wing ???