Lights on the wing
 

Ok, this might be a really daft question, however it's been bugging me for a while now. I've noticed when picking up my boyfriend from work, I watch the planes taking off and I've noticed it out of my window as well that some planes seem to have a flashing light on only one wing, I've seen one with both the other day which just made me wonder more!

Is it just so there isn't just a light but something to show it's a plane, or is there a reason why only one wing?

The flashing lights you are describing are most likely the strobe lights. There should be one on each wing and another set on the tail. This is in addition to the position lights (Green and Red) and beacon (red flashing - like a police car)

It may be that the aircraft you were looking at simply had one of the strobe lights burnt out, and that's why you only saw one.

Alternatively, there are certain aircraft designs which allow for the selection of specific strobe lights on and off (although this is more for military aircraft who will be flying in formation than for civilian aircraft). If this is the case, then it's simply a switch in the cockpit - one of the Dash-8's that I currently fly has this modification, and it is really easy to forget that instead of one switch, it's actually four that you need to check.

Lastly, these strobes, by regulation, need only be seen through a specific arc around the wing tip, so it may also be that you were just at an angle that did not allow you to see the other strobe.

In any case, the strobes are meant for visibility in the air, and it's accepted as best practice not to turn them on until you're on the runway - they're quite bright to look at during a taxi! In saying that, every operator has different criteria of when to turn them on and off, so I'm sure someone else will point that out! :)

I hope that helps!

Note: edit for grammar.

If you are referring to the white flashing strobes, they are anti-collision lights and have one on each wing tip.

Interesting, maybe I was just looking at them at an angle where I could only see one, however it seems to be pretty much every single one I've seen.
When they fly over they come straight at me then usually turn to my left and still only 1 flashing light.

Lizz, very good; this is important.

If you see a single flash, that is from a certain aircraft manufacturer's aircraft beginning with B.

Airbus aircraft have a double flash and those are the ones you want to be flying on.

I hope this helps.

Invicta Dc4
Anti collision lights are red and are found, one on top of fueslage and one on bottom of fuselage

Could it be the "anti-bird strike" lights that pulse the landing lights sometimes alternately?