The YouTube description claims this video was taken during a flight in January 23, 2012, by the commercial pilot Joseph Daniel Araya from Costa Rica. Araya claims that the object appeared on his cell phone screen while filming during flight, but went he actually looked outside the window he was not able to see anything, leaving us with a short video as the only evidence for this interesting UFO sighting.
The white flying object moves quite fast from left to right, in a way that corresponds with the position of the plane against the sun, a fact which might help to establish a light reflection theory, but also appeared to look like a solid body craft, and not smeared in any way, as sunlight would reflect.
I feel very positive towards this one, it was taken by a pilot during flight, wasn't seen by the naked eye which is logical considering the level of technology we are probably dealing with here, and is showing a configuration of an actual flying craft. I will update this post if further relevant information will surface.