There doesn't seem to be a good aerodynamical reason to change shape back and forth, and aliens are not entitled to their own laws of physics.
The most likely explanation is that the large airplane in foreground creates a lensing effect, as the airflow around it is quite significant - and it doesn't take more than a hot parking lot to see trees and parked cars "changing shape" behind it. But we don't really think that those objects are changing shape.
This UFO is probably just another airplane that goes much faster and much farther behind the one in foreground. It's hardly a surprise that there are airplanes around a major airport. An aircraft at takeoff is moving pretty slowly. Also a long-focus lens can flatten the distances quite a lot:
Comparing magnification by using a long lens to magnification by moving closer, however, the long-focus-lens shot appears to compress the distance between objects due to the perspective from the more distant location. Long lenses thus give a photographer an alternative to the type of perspective distortion exhibited by shorter focal length lenses where (when the photographer stands closer to the given subject) different portions of a subject in a photograph can appear out of proportion to each other.
LOL, who says it has anything to do with aerodynamics?
And as far as aliens are concerned, their appreciation of our understanding of the laws of physics could easily be as our appreciation of the understanding of physics by New Guinea headhunters.
After all, if the made it here from another star system, they already know more physics than we do.