Thanks very much for your exlanation.
On your chest x-ray a shadow is being seen in the right middle lobe. This could be due to atelectasis or infiltrate. Atelectasis is an area of the lung that is not receiving air. This is often referred to as a collapsed area of the lung. An infiltrate indicates that a biological substance generally not found in the lung has snuck in and now resides there. This could be caused by any of a number of lung diseases. Pneumonia is one example. You will need to check with your doctor to know what would be causing your infiltrate and the best treatment. A chest CT scan is more sensitive and shows more detail than a chest x-ray, so this may be the next test that is done.
This does not create any health risk to traveling across the country by plane.